Rustfmt

[little-dude]

Trying to run rusmft on libterm. It is work in progress, but since it's pretty big and it's my first ever rust contribution, I'd appreciate some feedback I tried to split that in small commits. The commit messages that contain [UNSURE] are those for which I'm not sure if rustfmt is right.

Thanks @nrc for giving newbies a chance to contribute to actual code :) I found a few issues in rustfmt doing this, I'll open issues soon.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @nikomatsakis (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. The way Github handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed.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.

[little-dude]

r? @nrc

[little-dude]

Geez I missed that someone else already started to work on the same thing at #28907 :( I'll look for another one.