[clang] [OpenMP] Add runtime selection for metadirective with non-constant conditions. (PR #192455)

[Zahira Ammarguellat via cfe-commits]

zahiraam wrote:

@alexey-bataev I made some changes to handle non-resolvable compile time condition and create the correct AST. I have removed the codegen code entirely from this PR. Please take a look and le me know what you think.

https://github.com/llvm/llvm-project/pull/192455