[clang] [flang] [llvm] [CLANG][OpenMP] Add support for OpenMP6.0 transparent clause (PR #166810)

[Zahira Ammarguellat via llvm-commits]

zahiraam wrote:

> OmpTransparentClause was added in #158149. It has the `IncompleteTrait` which is described as:
> 
> > // - IncompleteTrait: the class is a placeholder class that is currently empty,
> > //   but will be completed at a later time.
> 
> It probably is an integer instead of an enum just because it is work in progress.

@Meinersbur Thanks for getting back to me.
Here is an attempt to make the `transparent clause` take `OMP_*` arguments. Would you mind taking a look at the changes?

https://github.com/llvm/llvm-project/pull/166810