Stabilize pointer::align_offset

Closes #44488

Closes #44488

 Bootstrap x86_64 musl by itself

It should slightly reduce build time and prepares ground for musl native tests.

NOTE: I haven't tested artifacts yet (only the build).

Can I have double try?

r? @alexcrichton

Add a tidy check for files with over 3,000 lines

Files with a large number of lines can cause issues in GitHub (e.g. https://github.com/rust-lang/rust/issues/60015) and also tend to be indicative of opportunities to refactor into less monolithic structures.

This adds a new check to tidy to warn against files that have more than 3,000 lines, as suggested in https://github.com/rust-lang/rust/issues/60015#issuecomment-483868594. (This number was chosen fairly arbitrarily as a reasonable indicator of size.) This check can be ignored with `// ignore-tidy-filelength`.

Existing files with greater than 3,000 lines currently ignore the check, but this helps us spot when files are getting too large. (We might try to split up all files larger than this in the future, as in https://github.com/rust-lang/rust/issues/60015).

Rollup of 12 pull requests

Successful merges:

 - #59734 (Prevent failure in case no space left on device in rustdoc)
 - #59940 (Set cfg(test) when rustdoc is running with --test option)
 - #60134 (Fix index-page generation)
 - #60165 (Add Pin::{into_inner,into_inner_unchecked})
 - #60183 (Chalkify: Add builtin Copy/Clone)
 - #60225 (Introduce hir::ExprKind::Use and employ in for loop desugaring.)
 - #60247 (Implement Debug for Place using Place::iterate)
 - #60259 (Derive Default instead of new in applicable lint)
 - #60267 (Add feature-gate for f16c target feature)
 - #60284 (Do not allow const generics to depend on type parameters)
 - #60285 (Do not ICE when checking types against foreign fn)
 - #60289 (Make `-Z allow-features` work for stdlib features)

Failed merges:

r? @ghost

Make `-Z allow-features` work for stdlib features

r? @cramertj

Do not ICE when checking types against foreign fn

Fix #60275.

Do not allow const generics to depend on type parameters

Fixes https://github.com/rust-lang/rust/issues/60264. In https://github.com/rust-lang/rust/pull/58191/files/b534cf992d0189032207f395c27ed092c89b40c7#diff-aeb0880081a991f34aef2ab889e1fb7a, it was suggested that there might be a better place for this error, but as this bug already affects stable, it's probably worth merging this now, and refactoring afterwards (I can open an issue for this).

Add feature-gate for f16c target feature

r? @alexcrichton

Derive Default instead of new in applicable lint

Closes #60181

As far as I can see, at least within the `src/librustc_lint` directory this is the only place this is applicable.

Implement Debug for Place using Place::iterate

r? @oli-obk

Introduce hir::ExprKind::Use and employ in for loop desugaring.

In the `for $pat in $expr $block` desugaring we end with a `{ let _result = $match_expr; _result }` construct which makes `for` loops into a terminating scope and affects drop order. The construct was introduced in year 2015 by @pnkfelix in https://github.com/rust-lang/rust/pull/21984.

This PR replaces the construct with `hir::ExprKind::Use(P<hir::Expr>)` which is equivalent semantically but should hopefully be less costly in terms of compile time performance (to be determined).

This is extracted out of https://github.com/rust-lang/rust/pull/59288/commits/91b0abdfb23f980d2e5d5c30bc65ed8e95b04788 from https://github.com/rust-lang/rust/pull/59288 for easier review and so that the perf implications wrt. `for`-loops can be measured.

r? @oli-obk

Chalkify: Add builtin Copy/Clone

r? @nikomatsakis

Add Pin::{into_inner,into_inner_unchecked}

These functions are useful for unsafe code that needs to temporarily pull smart pointers out of the `Pin`, e.g. [the change that inspired them](https://github.com/Nemo157/futures-rs/commit/b4361780faf764c7cb046ed75f863a6fcfd44800#diff-1a4e0ba4d1b539412ca576411ec6c7c2R258) is taking a `Pin<Box<dyn Future>>`, turning it into a `*mut dyn Future` via `Box::into_raw(unsafe { Pin::into_inner_unchecked(pin) })` then later dropping this via `drop(Pin::from(Box::from_raw(ptr)))`. This can be accomplished today via `{ let ptr = unsafe { Pin::get_unchecked_mut(pin.as_mut()) } as *mut dyn Future; mem::forget(pin); ptr }`, but this is far more complicated and loses out on the symmetry of using `Box::into_raw` and `Box::from_raw`.

I'll extend the documentation on what guarantees `into_inner_unchecked` needs to uphold once I get some feedback on whether this API is wanted or not.

r? @withoutboats

Fix index-page generation

Fixes #60096.

The minifier was minifying crates name in `searchIndex` key position, which was a bit problematic for multiple reasons.

r? @rust-lang/rustdoc

Set cfg(test) when rustdoc is running with --test option

Following a [discussion on twitter](https://twitter.com/burntsushi5/status/1117091914199785473), I proposed this change. What do you think about it?

r? @QuietMisdreavus

cc @BurntSushi

Prevent failure in case no space left on device in rustdoc

Fixes #59703.

r? @QuietMisdreavus

Improved error message when type must be bound due to generator.

Fixes #58930.

Keen to get some feedback - is this as minimal as we can get it or is there an existing visitor I could repurpose?

Implement saturating_abs() and saturating_neg() functions for signed integer types

Similar to wrapping_abs() / wrapping_neg() functions but saturating at the numeric bounds instead of wrapping around. Complements the existing set of functions with saturation mechanics.

cc #59983

Error now mentions type var name and span is highlighted.

Similar to wrapping_abs() / wrapping_neg() functions but saturating at
the numeric bounds instead of wrapping around. Complements the existing
set of functions with saturation mechanics.

submodules: update clippy from 9897442f to 8c0e038f

Should fix clippy/rls toolstate breakage

Changes:
````
Rustup for https://github.com/rust-lang/rust/pull/59042
Update pulldown_cmark to 0.5
Only run AppVeyor on r+, try and the master branch
Remove approx_constant known problems
Suppress let_and_return if let has attributes
Add test for or_fun_call macro suggestion
UI test cleanup: Extract needless_range_loop tests
Change "if types change" to "if you later change the type"
````

r? @oli-obk

Changes:
````
Rustup for https://github.com/rust-lang/rust/pull/59042
Update pulldown_cmark to 0.5
Only run AppVeyor on r+, try and the master branch
Remove approx_constant known problems
Suppress let_and_return if let has attributes
Add test for or_fun_call macro suggestion
UI test cleanup: Extract needless_range_loop tests
Change "if types change" to "if you later change the type"
````