Add missing PartialEq impls for Vec and array

[fallofpheonix]

Fixes #149017.

This PR adds the missing PartialEq implementations between Vec<T> and [U; N], specifically:

• [T; N] == Vec<U>
• &[T; N] == Vec<U>
• &mut [T; N] == Vec<U>
• Vec<T> == &mut [U; N]

Tested locally by adding equality assertions in library/alloctests/tests/vec.rs.

Please let me know if any other adjustments are needed.

[rustbot]

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[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.

[bjorn3]

This seems like it could cause inference failures. Maybe needs a crater run?

[apiraino]

@fallofpheonix please do not trigger unprompted reviews from bots in our repository, thanks.

This was already pointed out in #156876 (comment)

[workingjubilee]

A pull request is already in flight for #149045 and this one will just lead to duplicating process because it overlaps.

Though why didn't a crater get run for that one...?

[fallofpheonix]

Closing in favor of the existing PR #149045 as pointed out by @workingjubilee. Thanks for the heads up, and apologies for the duplicate! Also, noted on the unprompted bot reviews (@apiraino) — I'll make sure not to trigger them in the future.