[clang] [clang][TableGen] Migrate clang-tblgen to use const RecordKeeper (PR #107533)

[Aaron Ballman via cfe-commits]

https://github.com/AaronBallman commented:

Thank you for this!

There's a fair amount of churn here as well as quite a few unrelated formatting changes. Would it be reasonable to split this up to make it a bit easier on reviewers?

0) Formatting changes (those are NFC and don't really require review at all)
1) Split the PRs based on what's being tablegenned (for instance, all the AST stuff at once, all the comment stuff at once, etc)

(Any other way of splitting things up is also fine, it's just a lot to sit down and pour through as one review.)

https://github.com/llvm/llvm-project/pull/107533