…ing normalization.

The old struct tail functions did not deal with `<T as Trait>::A` and `impl
Trait`, at least not explicitly. (We didn't notice this bug before because it
is only exposed when the tail (post deep normalization) is not `Sized`, so it
was a rare case to deal with.)

For post type-checking (i.e. during codegen), there is now
`struct_tail_erasing_lifetimes` and `struct_lockstep_tails_erasing_lifetimes`,
which each take an additional `ParamEnv` argument to drive normalization.

For pre type-checking cases where normalization is not needed, there is
`struct_tail_without_normalization`. (Currently, the only instance of this is
`Expectation::rvalue_hint`.)

All of these new entrypoints work by calling out to common helper routines.
The helpers are parameterized over a closure that handles the normalization.

In developing rust-lang#61557 I noticed that there were two parts of our tools
that were rebuilt twice on CI. One was rustfmt fixed in rust-lang#61557, but
another was Cargo. The actual fix for Cargo's double compile was
rust-lang/cargo#7010 and took some time to propagate here. In an effort
to continue to assert that Cargo is itself not compiled twice, I updated
the assertion in rustbuild at the time of working on rust-lang#61557 but couldn't
land it because the fix wouldn't be ready until the next bootstrap.

The next bootstrap is now here, so the fix can now land! This does not
change the behavior of rustbuild but it is intended to catch the
previous iteration of compiling cargo twice. The main update here was to
consider more files than those in `$target/release/deps` but also
consider those in `$target/release`. That's where, for example,
`libcargo.rlib` shows up and it's the file we learn about, and that's
what we want to deduplicate.

Add an AtomicCell abstraction

Split out from rust-lang#61923.

…il-normalize-when-possible, r=eddyb

Make struct_tail normalize when possible

As noted in commit message: this replaces the existing methods to extract the struct tail(s) with new entry points that make the handling of normalization explicit.

Most of the places that call `struct_tail` are during codegen, post type-checking, and therefore they can get away with using `tcx.normalize_erasing_regions` (this is the entry point `struct_tail_erasing_lifetimes`)

For other cases that may arise, one can use the core method, which is parameterized over the normalization `Ty -> Ty` closure (`struct_tail_with_normalize`).

Or one can use the trivial entry point that does not normalization (`struct_tail_without_normalization`)

----

I spent a little while trying to make a test that exposed the bug via `impl Trait` rather than a projection, but I failed to find something that tripped up the current nightly `rustc`.
 * I have *not* spent any time trying to make tests that trip up the other places where `struct_tail` was previously being called. While I do think the task of making such tests could be worthwhile, I am simply running out of time. (Its also possible that the layout code is always the first point called, and thus it may be pointless to try to come up with such tests.)

I also spent a little time discussing with @eddyb where this code should live. They suggested moving `struct_tail` and its sibling `struct_lockstep_tails` to the `LayoutCx`.  But in the interest of time, I have left that refactoring (which may be questionable at this point) to a follow-up task.

----

Fix rust-lang#60431

Handle errors during error recovery gracefully

Fix rust-lang#62546.

…e, r=Mark-Simulacrum

rustbuild: Improve assert about building tools once

In developing rust-lang#61557 I noticed that there were two parts of our tools
that were rebuilt twice on CI. One was rustfmt fixed in rust-lang#61557, but
another was Cargo. The actual fix for Cargo's double compile was
rust-lang/cargo#7010 and took some time to propagate here. In an effort
to continue to assert that Cargo is itself not compiled twice, I updated
the assertion in rustbuild at the time of working on rust-lang#61557 but couldn't
land it because the fix wouldn't be ready until the next bootstrap.

The next bootstrap is now here, so the fix can now land! This does not
change the behavior of rustbuild but it is intended to catch the
previous iteration of compiling cargo twice. The main update here was to
consider more files than those in `$target/release/deps` but also
consider those in `$target/release`. That's where, for example,
`libcargo.rlib` shows up and it's the file we learn about, and that's
what we want to deduplicate.

…r=petrochenkov

Make some rustc macros more hygienic