core: Remove some redundant {}s from the sorting code

Remove deprecated and unstable slice_partition_at_index functions

They have been deprecated since commit 01ac5a97
which was part of the 1.49.0 release, so from the point of nightly,
11 releases ago.

unix: Use metadata for `DirEntry::file_type` fallback

When `DirEntry::file_type` fails to match a known `d_type`, we should
fall back to `DirEntry::metadata` instead of a bare `lstat`, because
this is faster and more reliable on targets with `fstatat`.

Document `SystemTime` platform precision

Fixes #88822

Accommodate yield points in the format_args expansion

Fixes #93274.

For the case `println!("{} {:?}", "", async {}.await)` in the issue, the expansion before:

```rust
::std::io::_print(
    ::core::fmt::Arguments::new_v1(
        &["", " ", "\n"],
        &[
            ::core::fmt::ArgumentV1::new(&"", ::core::fmt::Display::fmt),
            ::core::fmt::ArgumentV1::new(&async {}.await, ::core::fmt::Debug::fmt),
        ],
    ),
);
```

After:

```rust
::std::io::_print(
    ::core::fmt::Arguments::new_v1(
        &["", " ", "\n"],
        &match (&"", &async {}.await) {
            _args => [
                ::core::fmt::ArgumentV1::new(_args.0, ::core::fmt::Display::fmt),
                ::core::fmt::ArgumentV1::new(_args.1, ::core::fmt::Debug::fmt),
            ],
        },
    ),
);
```

review the total_cmp documentation

The documentation has been restructured to split out a brief summary
paragraph out from the following elaborating paragraphs.

I also attempted my hand at wording improvements and adding articles
where I felt them missing, but being non-native english speaker these
may need more thorough review.

cc https://github.com/rust-lang/rust/issues/72599

Improve suggestion for escaping reserved keywords

r? `@davidtwco`

Create `core::fmt::ArgumentV1` with generics instead of fn pointer

Split from (and prerequisite of) #90488, as this seems to have perf implication.

`@rustbot` label: +T-libs

The documentation has been restructured to split out a brief summary
paragraph out from the following elaborating paragraphs.

I also attempted my hand at wording improvements and adding articles
where I felt them missing, but being non-native english speaker these
may need more thorough review.

rustdoc: Remove `def_id_no_primitives`

Fixes #90187.

Currently fails with:

    error: future cannot be sent between threads safely
      --> $DIR/src/test/ui/fmt/format-with-yield-point.rs:21:17
       |
    LL |     assert_send(with_await());
       |                 ^^^^^^^^^^^^ future returned by `with_await` is not `Send`
       |
       = help: the trait `Sync` is not implemented for `core::fmt::Opaque`
    note: future is not `Send` as this value is used across an await
      --> $DIR/src/test/ui/fmt/format-with-yield-point.rs:11:37
       |
    LL |     println!("{} {:?}", "", async {}.await);
       |     --------------------------------^^^^^^-
       |     |                               |
       |     |                               await occurs here, with `$crate::format_args_nl!($($arg)*)` maybe used later
       |     has type `ArgumentV1<'_>` which is not `Send`
       |     `$crate::format_args_nl!($($arg)*)` is later dropped here
    note: required by a bound in `assert_send`
      --> $DIR/src/test/ui/fmt/format-with-yield-point.rs:18:24
       |
    LL | fn assert_send(_: impl Send) {}
       |                        ^^^^ required by this bound in `assert_send`

    error: future cannot be sent between threads safely
      --> $DIR/src/test/ui/fmt/format-with-yield-point.rs:22:17
       |
    LL |     assert_send(with_macro_call());
       |                 ^^^^^^^^^^^^^^^^^ future returned by `with_macro_call` is not `Send`
       |
       = help: the trait `Sync` is not implemented for `core::fmt::Opaque`
    note: future is not `Send` as this value is used across an await
      --> $DIR/src/test/ui/fmt/format-with-yield-point.rs:6:17
       |
    LL |         async {}.await
       |                 ^^^^^^ await occurs here, with `$crate::format_args_nl!($($arg)*)` maybe used later
    ...
    LL |     println!("{} {:?}", "", m!());
       |     -----------------------------
       |     |                       |
       |     |                       in this macro invocation
       |     has type `ArgumentV1<'_>` which is not `Send`
       |     `$crate::format_args_nl!($($arg)*)` is later dropped here
    note: required by a bound in `assert_send`
      --> $DIR/src/test/ui/fmt/format-with-yield-point.rs:18:24
       |
    LL | fn assert_send(_: impl Send) {}
       |                        ^^^^ required by this bound in `assert_send`
       = note: this error originates in the macro `m` (in Nightly builds, run with -Z macro-backtrace for more info)

    error: aborting due to 2 previous errors

Rollup of 5 pull requests

Successful merges:

 - #92887 (Bootstrap compiler update)
 - #92908 (Render more readable macro matcher tokens in rustdoc)
 - #93183 (rustdoc: mobile nav fixes)
 - #93192 (Add VS 2022 into error message)
 - #93475 (Add test to ensure that theme is applied correctly when going back in history)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Add test to ensure that theme is applied correctly when going back in history

Fixes #93258.

r? `@jsha`

Add VS 2022 into error message

rustdoc: mobile nav fixes

- Make sure the mobile-topbar doesn't overflow its height if the user sets a bigger font.

- Make sure the sidebar can be scrolled all the way to the bottom by shortening it to accommodate the mobile-topbar.

- Make the item name in the mobile-topbar clickable to go to the top of the page.

- Remove excess padding sidebar in mobile mode.

Demo https://rustdoc.crud.net/jsha/mobile-nav-fixes/std/string/struct.String.html

r? `@GuillaumeGomez`

Render more readable macro matcher tokens in rustdoc

Follow-up to #92334.

This PR lifts some of the token rendering logic from https://github.com/dtolnay/prettyplease into rustdoc so that even the matchers for which a source code snippet is not available (because they are macro-generated, or any other reason) follow some baseline good assumptions about where the tokens in the macro matcher are appropriate to space.

The below screenshots show an example of the difference using one of the gnarliest macros I could find. Some things to notice:

- In the **before**, notice how a couple places break in between `$(....)`↵`*`, which is just about the worst possible place that it could break.

- In the **before**, the lines that wrapped are weirdly indented by 1 space of indentation relative to column 0. In the **after**, we use the typical way of block indenting in Rust syntax which is put the open/close delimiters on their own line and indent their contents by 4 spaces relative to the previous line (so 8 spaces relative to column 0, because the matcher itself is indented by 4 relative to the `macro_rules` header).

- In the **after**, macro_rules metavariables like `$tokens:tt` are kept together, which is how just about everybody writing Rust today writes them.

## Before

![Screenshot from 2022-01-14 13-05-53](https://user-images.githubusercontent.com/1940490/149585105-1f182b78-751f-421f-a234-9dbc04fa3bbd.png)

## After

![Screenshot from 2022-01-14 13-06-04](https://user-images.githubusercontent.com/1940490/149585118-d4b52ea7-3e67-4b6e-a12b-31dfb8172f86.png)

r? `@camelid`

Bootstrap compiler update

r? ``@Mark-Simulacrum``

They have been deprecated since commit 01ac5a97
which was part of the 1.49.0 release, so from the point of nightly,
11 releases ago.

Rollup of 8 pull requests

Successful merges:

 - #93256 (Make `join!` description more accurate)
 - #93358 (Add note suggesting that predicate may be satisfied, but is not `const`)
 - #93362 (Do not register infer var for GAT projection in RPIT)
 - #93391 (rustdoc: remove tooltip from source link)
 - #93414 (Move unstable is_{arch}_feature_detected! macros to std::arch)
 - #93441 (rustdoc: load the set of in-scope traits for modules with no docstring)
 - #93459 (fs: Don't copy d_name from struct dirent)
 - #93463 (Rename _args -> args in format_args expansion)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

- Make sure the mobile-topbar doesn't overflow its height if the user
  sets a bigger font.

- Make sure the sidebar can be scrolled all the way to the bottom by
  shortening it to accommodate the mobile-topbar.

- Make the item name in the mobile-topbar clickable to go to the top of
  the page.

- Remove excess padding sidebar in mobile mode.

When `DirEntry::file_type` fails to match a known `d_type`, we should
fall back to `DirEntry::metadata` instead of a bare `lstat`, because
this is faster and more reliable on targets with `fstatat`.

Rename _args -> args in format_args expansion

As observed in https://github.com/rust-lang/rust/pull/91359#discussion_r786058960, prior to that PR this variable was sometimes never used, such as in the case of:

```rust
println!("");

// used to expand to:
::std::io::_print(
    ::core::fmt::Arguments::new_v1(
        &["\n"],
        &match () {
            _args => [],
        },
    ),
);
```

so the leading underscore in `_args` was used to suppress an unused variable lint. However after #91359 the variable is always used when present, as the unused case would instead expand to:

```rust
::std::io::_print(::core::fmt::Arguments::new_v1(&["\n"], &[]));
```

fs: Don't copy d_name from struct dirent

The dirent returned from readdir() is only guaranteed to be valid for
d_reclen bytes on common platforms.  Since we copy the name separately
anyway, we can copy everything except d_name into DirEntry::entry.

Fixes #93384.

rustdoc: load the set of in-scope traits for modules with no docstring

Fixes #93428

This fix is a response to a couple of special cases related to the `module_id`, which is eventually used for trait candidates:

  * The module id is always set to the current crate, when checking `crate::`.

    Normally, the set of in-scope traits would be set in `load_links_in_attrs`, but if there are no doc comments, then that loop will never run.

  * the module id is set to the parent module, when resolving a module that is spelled like this:

        // Notice how we use an outlined doc comment here!
        // [`Test::my_fn`]
        mod something {
        }

    As with the above problem with `crate::`, we need to make sure the module gets its traits in scope resolved, even if it has no doc comments of its own.

Move unstable is_{arch}_feature_detected! macros to std::arch

These macros are unstable, except for `is_x86_feature_detected` which is still exported from the crate root for backwards-compatibility.

This should unblock the stabilization of `is_aarch64_feature_detected`.

r? ```@m-ou-se```

rustdoc: remove tooltip from source link

This made more sense back when it was abbreviated, but now it seems redundant.

Do not register infer var for GAT projection in RPIT

Fixes #93340
Fixes #91603

r? ```@oli-obk```

Add note suggesting that predicate may be satisfied, but is not `const`

Not sure if we should be printing this in addition to, or perhaps _instead_ of the help message:
```
help: the trait `~const Add` is not implemented for `NonConstAdd`
```

Also added `ParamEnv::is_const` and `PolyTraitPredicate::is_const_if_const` and, in a separate commit, used those in other places instead of `== hir::Constness::Const`, etc.

r? ````@fee1-dead````

Make `join!` description more accurate

The dirent returned from readdir() is only guaranteed to be valid for
d_reclen bytes on common platforms.  Since we copy the name separately
anyway, we can copy everything except d_name into DirEntry::entry.

Fixes #93384.

Rollup of 8 pull requests

Successful merges:

 - #88205 (Add Explanation For Error E0772)
 - #92274 (Add `intrinsics::const_deallocate`)
 - #93236 (Make `NonNull::new` `const`)
 - #93299 (Fix dot separator when there is no source link)
 - #93410 (kmc-solid: Implement `net::FileDesc::duplicate`)
 - #93424 (fix nit)
 - #93431 (remove unused `jemallocator` crate)
 - #93453 (Add GUI theme change test)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

This will prevent unstable order when HirIds are pertubated.