[clang] [Clang] Refactor the tests to be more uniform (PR #191944)

[Aaron Ballman via cfe-commits]

https://github.com/AaronBallman commented:

I'm a bit confused about the changes happening here because I don't understand why the triple needs to change on the test; this looks like we're trading x86 test coverage for x64 test coverage so I would have expected an additional RUN line rather than a change to it. So I'm probably missing something.

Would you mind updating the patch summary to explain why the changes are happening?

https://github.com/llvm/llvm-project/pull/191944