[flang][OpenMP] Add semantic checks for occurrence of nested Barrier regions

This patch adds the following nesting check for `barrier` constructs:

```
A barrier region may not be closely nested inside a worksharing, loop, task, taskloop, critical, ordered, atomic, or master region.
```

Also adds a test case for the check,

Reviewed By: kiranchandramohan

Differential Revision: https://reviews.llvm.org/D99888