Use `ResultsCursor` for `elaborate_drops`

Some cleanup after #68241. The old code was using a custom cursor-like struct called `InitializationData`.

Record proc macro harness order for use during metadata deserialization

Fixes #68690

When we generate the proc macro harness, we now explicitly recorder the
order in which we generate entries. We then use this ordering data to
deserialize the correct proc-macro-data from the crate metadata.

Struct variant field search

Fixes #16017.

Reopening of #64724.

cc @tomjakubowski
cc @ollie27

r? @kinnison

Fixes #68690

When we generate the proc macro harness, we now explicitly recorder the
order in which we generate entries. We then use this ordering data to
deserialize the correct proc-macro-data from the crate metadata.

add regression test for issue #68794

This is a minimal regression test for the issue #68794: "TEXTREL in
i686", which was fixed with e86019c4.

The test links a minimal rust static library into a shared library, and
checks that the linker didn't have to add the TEXTREL flag.

Rollup of 6 pull requests

Successful merges:

 - #64069 (Added From<Vec<NonZeroU8>> for CString)
 - #66721 (implement LowerExp and UpperExp for integers)
 - #69106 (Fix std::fs::copy on WASI target)
 - #69154 (Avoid calling `fn_sig` on closures)
 - #69166 (Check `has_typeck_tables` before calling `typeck_tables_of`)
 - #69180 (Suggest a comma if a struct initializer field fails to parse)

Failed merges:

r? @ghost

Suggest a comma if a struct initializer field fails to parse

Currently, we emit a "try adding a comma" suggestion if a comma is
missing in a struct definition. However, we emit no such suggestion if a
comma is missing in a struct initializer.

This commit adds a "try adding a comma" suggestion when we don't find a
comma during the parsing of a struct initializer field.

The change to `src/test/ui/parser/removed-syntax-with-1.stderr` isn't
great, but I don't see a good way of avoiding it.

Check `has_typeck_tables` before calling `typeck_tables_of`

Fixes #68684

r? @matthewjasper

Avoid calling `fn_sig` on closures

Fixes #68060

r? @petrochenkov

Fix std::fs::copy on WASI target

Previously `std::fs::copy` on wasm32-wasi would reuse code from the `sys_common` module and would successfully copy contents of the file just to fail right before closing it.

This was happening because `sys_common::copy` tries to copy permissions of the file, but permissions are not a thing in WASI (at least yet) and `set_permissions` is implemented as an unconditional runtime error.

This change instead adds a custom working implementation of `std::fs::copy` (like Rust already has on some other targets) that doesn't try to call `set_permissions` and is essentially a thin wrapper around `std::io::copy`.

Fixes #68560.

implement LowerExp and UpperExp for integers

Addresses https://github.com/rust-lang/rust/issues/39479

This implementation is heavily based on the preexisting `macro_rules! impl_Display` in the same file. I don't like the liberal use of unsafe in that macro and would like to modify it so `unsafe` is only present where necessary. What is Rust's policy on doing such modifications?

Also, I couldn't figure out where to put tests, can I have some help with that?

Added From<Vec<NonZeroU8>> for CString

Added a `From<Vec<NonZeroU8>>` `impl` for `CString`

# Rationale

  - `CString::from_vec_unchecked` is a subtle function, that makes `unsafe` code harder to audit when the generated `Vec`'s creation is non-trivial. This `impl` allows to write safer `unsafe` code thanks to the very explicit semantics of the `Vec<NonZeroU8>` type.

  - One such situation is when trying to `.read()` a `CString`, see issue #59229.

      - this lead to a PR: #59314, that was closed for being too specific / narrow (it only targetted being able to `.read()` a `CString`, when this pattern could have been generalized).

     - the issue suggested another route, based on `From<Vec<NonZeroU8>>`, which is indeed a less general and more concise code pattern.

  - quoting @shnatsel:

      - >  For me the main thing about making this safe is simplifying auditing - people have spent like an hour looking at just this one unsafe block in libflate because it's not clear what exactly is unchecked, so you have to look it up when auditing anyway. This has distracted us from much more serious memory safety issues the library had.
Having this trivial impl in stdlib would turn this into safe code with compiler more or less guaranteeing that it's fine, and save anyone auditing the code a whole lot of time.

Currently, we emit a "try adding a comma" suggestion if a comma is
missing in a struct definition. However, we emit no such suggestion if a
comma is missing in a struct initializer.

This commit adds a "try adding a comma" suggestion when we don't find a
comma during the parsing of a struct initializer field.

The change to `src/test/ui/parser/removed-syntax-with-1.stderr` isn't
great, but I don't see a good way of avoiding it.

Infer regions for opaque types in borrowck

This is a step towards the goal of typeck not doing region inference.

The commits up to `Arena allocate the result of mir_borrowck` are various bug fixes and prerequisites.
The remaining commits move opaque type inference to borrow checking.

r? @nikomatsakis

Rollup of 7 pull requests

Successful merges:

 - #68129 (Correct inference of primitive operand type behind binary operation)
 - #68475 (Use a `ParamEnvAnd<Predicate>` for caching in `ObligationForest`)
 - #68856 (typeck: clarify def_bm adjustments & add tests for or-patterns)
 - #69051 (simplify_try: address some of eddyb's comments)
 - #69128 (Fix extra subslice lowering)
 - #69150 (Follow-up to #68848)
 - #69164 (Update pulldown-cmark dependency)

Failed merges:

r? @ghost

This ensures that NLL will infer suitable values for regions in opaque
types when it's possible.

Also correctly calculate what the upper bounds are.

* Use better span for member constraint errors
* Avoid a bad suggestion
* Don't report member constraint errors if we have other universal
  region errors.

We want type checking for function bodies to ignore/erase regions. As
such, we need to infer the regions in opaque types in borrow check
instead.

Update pulldown-cmark dependency

r? @kinnison

cc @ollie27

Reopening of  #65894.