[clang] [StrTable] Mechanically convert NVPTX builtins to use TableGen (PR #122873)

[Artem Belevich via cfe-commits]

https://github.com/Artem-B approved this pull request.

LGTM overall with a couple of nits.

I like the direction of the change. Tablegen is probably a better way to handle NVPTX quirks, than a preprocessor. We may finally be able to replace the string-based constraints that are growing a bit too long already with something more flexible (custom code blocks similar to LLVM's constraints + sensible error message generation to go along with them)

https://github.com/llvm/llvm-project/pull/122873