[flang][OpenMP] Add semantic checks for ordered construct

This patch implements the following semantic checks according to
OpenMP Version 5.1 Ordered construct restriction:

```
At most one threads clause can appear on an ordered construct; At most
one simd clause can appear on an ordered construct; At most one
depend(source) clause can appear on an ordered construct; Either
depend(sink:vec) clauses or depend(source) clauses may appear on an
ordered construct, but not both.
```

This patch also implements the following semantic checks according to
the syntax and descriptions in OpenMP Version 5.1 Ordered construct:

```
The dependence types of sink or source are only allowed on an ordered
construct. The depend(*) clauses are not allowed when ordered construct
is a block construct with an ordered region. The threads or simd clauses
are not allowed when the ordered construct is a standalone construct
with no ordered region.
```

Co-authored-by: Sameeran Joshi <sameeranjayant.joshi@amd.com>

Reviewed By: kiranchandramohan

Differential Revision: https://reviews.llvm.org/D108512