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

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mikaelholmen wrote:

> @mikaelholmen Thanks. I've fixed the signature in [e099e7b](https://github.com/llvm/llvm-project/commit/e099e7b278c774338c7019e38fbbca9ef2c8dd74).

Thanks.
Seems like we're missing testcases though if a bug like that passes lit tests without errors.

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