Rust: add rust-analyzer update instructions

[geoffw0]

First commit (most of the work) is taken from closed PR #19930 by @redsun82 .

I hope to add a few more details before this is ready to merge.

[Copilot]

Pull Request Overview

This PR adds comprehensive documentation for updating rust-analyzer dependencies in the Rust CodeQL implementation. The changes provide step-by-step instructions for maintaining rust-analyzer and related dependencies, including toolchain updates and schema migrations.

• Adds a detailed section on rust-analyzer update procedures
• Includes instructions for dependency management, bazel file regeneration, and toolchain updates
• Documents the complete workflow from upgrade to testing and schema migration

[redsun82]

LGTM, apart from a minor oversight coming from me 🙂

[redsun82]

The CI failures should go away with the merge from main I just did

[paldepind]

Looks good to me. Instructions are clear and easy to follow. Thanks @geoffw0 and @redsun82.

One thought going forward, in #20408 I ran into a problem because the first cargo upgrade also applies to ruby/extractor/Cargo.toml and that broke the Ruby extractor. I guess it would be preferable if we could update RA for the Rust extractor without affecting the Ruby extractor.

[aibaars]

One thought going forward, in #20408 I ran into a problem because the first cargo upgrade also applies to ruby/extractor/Cargo.toml and that broke the Ruby extractor. I guess it would be preferable if we could update RA for the Rust extractor without affecting the Ruby extractor.

Fair point, although it is a nice side effect that the Ruby extractor is kept up to date as well.

[geoffw0]

Merging - but I'm happy to make further changes to these instructions if there are more suggestions.