chore: update tree-sitter-rust to v0.21.0

[pedromfedricci]

Updates tree-sitter-rust to v0.21.0. There were a number of changes since 0.20.3 (diff). The only breaking change (commit) that I found was renaming loop_label node to label, which is addressed in the highlights.scm file. I haven't experienced any regressions, but it would be great if other people could try it out too before merging.

[archseer]

Doc comments are now also finally exposed as a query tree-sitter/tree-sitter-rust@v0.20.3...v0.21.0#diff-d485a982e458ef8da2cc203585065b7542665cb80b78d230b1e8f77ea25825d4

[the-mikedavis]

We may want to add that injection later though, see #9695

Also see #9695 for the changes to fix the test cases. We use tree-sitter-rust in some unit tests in helix-core

[pedromfedricci]

Hmm my bad, I checked for open PRs related tree-sitter-rust and didn't realize that #9695 draft was related. I will fix the test cases.

[archseer]

We can probably just merge #9695.

[pedromfedricci]

Yeah this is pretty much covered by #9695 if you prefer to close this one and wait/merge the other.

[pascalkuthe]

We can probably just merge #9695.

The problem mentioned there regarding combined I jects is quite noticeable unfortunately and I looked into it, a fix is not trivial

[the-mikedavis]

Updating the grammar is a kind of side quest for #9695 anyways, I'd be happy to rebase on this change and get any fixes in the newer version on master faster