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

[Chandler Carruth via cfe-commits]

chandlerc wrote:

> ⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

Note that the PR doesn't actually change the lines that `clang-format` changes here, and the `clang-format` change makes these lines inconsistent with the rest of the file, so I intentionally did not apply these formatting changes. My guess was that the community would prefer to not have deviations from the surrounding file introduced like this.

If instead folks would prefer me to apply the changes from `clang-format`, happy to do so. Just let me know.

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