[clang] [CIR][OpenMP] Add support for combined target parallel directives (PR #207019)

[Sergio Afonso via cfe-commits]

https://github.com/skatrak commented:

Thank you Jan, lowering looks good minus some small comments. I think it should be fine to introduce the construct decomposition logic as part of the patch, but I'll probably defer reviewing that part to @kparzysz, who can do a much better job at that than myself.

https://github.com/llvm/llvm-project/pull/207019