[clang] [clang][TableGen] Change ASTTableGen to use const Record pointers (PR #108193)

[Rahul Joshi via cfe-commits]

jurahul wrote:

@AaronBallman I am adding you as a reviewer, but if there is someone else who can help review these, please let me know.

https://github.com/llvm/llvm-project/pull/108193