[clang] [Clang] [NFC] Introduce `DynamicRecursiveASTVisitor` (PR #110040)

[Aaron Ballman via cfe-commits]

https://github.com/AaronBallman commented:

Thank you for working on this! Do you have some performance numbers you can share which sells us on the changes?

https://github.com/llvm/llvm-project/pull/110040