Add serial tests

[shivjm]

This PR adds a #[serial] attribute that marks tests that should be executed one-by-one rather than concurrently (per #33519).

I’ve confirmed that the libtest tests pass. I wasn’t able to run the full suite as a lot of the run_make tests seem to fail on my Windows system, but everything passed up to that point. I also ran a tidy check and fixed a couple of small errors.

Rust (and PR!) newbie here, so please do let me know if I’m doing something poorly or incorrectly!

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @brson (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

[shivjm]

Just realized I had forgotten to commit the tidy fixes.

[arielb1]

Thanks for the PR @shivjm! @brson (or someone else) will be reviewing your PR soon.

[shivjm]

I managed to discover a new way to mess up history by rewriting metadata, so this pull request is in a strange spot right now. Would it be a problem if I closed this PR and opened a new one from a different branch with the same result, only a little cleaner? (Apologies, again, for how new I am at this.)

[Mark-Simulacrum]

No problem at all! Let us know if there is anything we can help with, feel free to reach out over IRC too, if you want.

[shivjm]

Cheers!