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

[Michael Kruse via llvm-commits]

Meinersbur 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. 

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