[clang] [clang-tools-extra] [llvm] [clang] Refactor Builtins.def to be a tablegen file (PR #68324)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> I've found few differences w.r.t. the previous builtins definition. If the change was intended to be a NFC then they might be considered issues.

Thank you for catching those; this was intended as an NFC change, so I think these are bugs.

https://github.com/llvm/llvm-project/pull/68324