[flang] [llvm] [flang][OpenMP] Decompose compound constructs, do recursive lowering (PR #90098)

[Krzysztof Parzyszek via llvm-commits]

kparzysz wrote:

> ```
> teams.f90
> ```
There is an `if` clause on the `teams` directive: this is only allowed in OpenMP 5.2 or later (https://github.com/llvm/llvm-project/pull/92180).

https://github.com/llvm/llvm-project/pull/90098