miri: enforce proper types for c-variadic arguments in shims

[RalfJung]

This adds proper type checks for c-variadic argument handling in Miri shims. So far we would have ICEd for many type mismatches since the innards of the interpreter generally assume that things are well-typed. The checks are are using are the same as for next_arg.

This uncovered some interesting points:

• We should accept &mut as equivalent to *mut. We don't allow &mut as a type in next_arg but we do allow it for c-variadic calls, so this change also affects a bit more code in const-eval (if the caller passes an &mut and the callee expects a *mut). Even CFI is okay with treating &mut and *mut as equivalent so this should be fine. Cc @folkertdev
• Some places in the standard library futex handling used types for their variadic arguments that are not quite correct according to these rules. I fixed those. Cc @m-ou-se
• One variadic function takes pointers to libc::timespec. A program with a libc dependency has two copies of libc (one in the sysroot, and the normal dependency), leading to Miri seeing a type mismatch. C generally considers two copies of the same type to be identical, so I implemented logic that does the same: the names of the type, and the names and types of all fields, must be identical. I then also used that logic for the normal ABI checks, where it will also help since we had similar trouble there in the past (that we had to find other work-arounds for).

[rustbot]

Some changes occurred to the CTFE / Miri interpreter

cc @rust-lang/miri

These commits modify the Cargo.lock file. Unintentional changes to Cargo.lock can be introduced when switching branches and rebasing PRs.

If this was unintentional then you should revert the changes before this PR is merged.
Otherwise, you can ignore this comment.

miri is developed in its own repository. If the Miri part of this change can be broken out, consider making this change to rust-lang/miri instead. However, if Miri needs adjusting for rustc changes, just ignore this message.

cc @rust-lang/miri

Some changes occurred to the CTFE machinery

cc @oli-obk, @lcnr

Some changes occurred to the CTFE / Miri interpreter

cc @rust-lang/miri, @oli-obk, @lcnr

[rustbot]

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[RalfJung]

r? @saethlin

[RalfJung]

@bors try jobs=aux

[rust-bors]

☀️ Try build successful (CI)
Build commit: 7980ab1 (7980ab1bb9a58e8bf9c45898865099a8d7564457)
Base parent: cc05892 (cc05892c8346313865afd91ca12ee1fde6d3603c)

[rustbot]

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.