[clang] nonblocking/nonallocating attributes: 2nd pass caller/callee analysis (PR #99656)

[Erich Keane via cfe-commits]

https://github.com/erichkeane commented:

First, thank you so much @Sirraide for doing such a thorough review here!  I've been buried lately, so knowing you were taking care of this was really appreciated!

Second, this patch looks really close! I have a couple of quick/small comments.  The ReadDeclID changing the ID seems odd, but otherwise its just documentation/comment requests.

https://github.com/llvm/llvm-project/pull/99656