[flang] [llvm] [Flang][OpenMP] Add semantic checks for order clause (PR #115281)

[Kiran Chandramohan via llvm-commits]

kiranchandramohan wrote:

Regions in OpenMP are generally dynamic (and not static). Will the checks work across function/subroutine calls?

```
subroutine omp_order_runtime_api_call_01()
    integer :: i
    !$omp do order(concurrent)
    do i = 1, 5
      call myf()        
    end do
    !$omp end do
contains
  subroutine myf
    print*, omp_get_thread_num()
  end subroutine
end subroutine omp_order_runtime_api_call_01
```

https://github.com/llvm/llvm-project/pull/115281