[clang] [Clang] [Parser] Support [[omp::assume]] (PR #84582)

[Alexey Bataev via cfe-commits]

alexey-bataev wrote:

> One more thing: this is just a different spelling for what was previously already exposed as `__attribute__((assume))`; I’m not sure if/how familiar you are with that one, but I hope its semantics align with what `[[omp::assume]]` is supposed to do. I’m asking because I’m not terribly familiar with OpenMP myself.

Some details about assume directive

https://www.openmp.org/wp-content/uploads/OpenMP-assume_Doerfert.pdf

https://github.com/llvm/llvm-project/pull/84582