[openmp] [llvm] [clang] [OpenMP] Introduce support for OMPX extensions and taskgraph frontend (PR #66919)

[Jose Manuel Monsalve Diaz via cfe-commits]

josemonsalve2 wrote:

Sorry, @alexey-bataev, some were marked as resolved, and we did not see them.

The wording on my previous question needed to be corrected, too. I did not mean to ask if this is ready to land as is but instead if the division of the original PR into just this front-end part is what you would suggest we do. 

https://github.com/llvm/llvm-project/pull/66919