[clang] [X86][RFC] Refactor the SSE intrinsics constexpr tests to simplify future expansion (PR #112578)

[Aiden Grossman via cfe-commits]

https://github.com/boomanaiden154 approved this pull request.

This seems reasonable enough modulo refactoring test macros to a common spot if reasonable.

This is certainly a lot cleaner than throwing all the constant expression tests at the end of the file.

https://github.com/llvm/llvm-project/pull/112578