[clang] [BoundsSafety] Late-parse counted_by on parameters and callback return types (PR #230581)

[Hans Wennborg via cfe-commits]

zmodem wrote:

> only the last one, "[BoundsSafety] Late-parse counted_by on parameters and callback return types",
is new here.

Looking at only this commit, it's still very large. Is there any chance it could be broken up, so it can be reviewed and landed more gradually?

https://github.com/llvm/llvm-project/pull/230581