[clang] [HLSL] standardize builtin unit tests (PR #83340)

[Justin Bogner via cfe-commits]

bogner wrote:

If we want to talk about guidelines for clang-formatting tests in general we should probably bring it up with the wider LLVM community on discourse. The de facto standard today is that tests should be well formatted like anything else unless there's a good reason not to, but this isn't written down or strongly enforced as far as I know. It might be worth bringing it up to the community to change the test folder .clang-format configs to just disable reflow comments - as far as I can tell that'd be a net positive.

https://github.com/llvm/llvm-project/pull/83340