[clang] [llvm] [clang][NVPTX] Add builtins and intrinsics for conversions of new FP types (PR #134345)

[Srinivasa Ravi via cfe-commits]

Wolfram70 wrote:

Added `-disable-llvm-optzns` to the new RUN lines in `builtins-nvptx.c` since I think some tests are failing due to changes from #134416 

https://github.com/llvm/llvm-project/pull/134345