[MLIR][OpenMP] Enable BlockArgOpenMPOpInterface accessing operands (#130769)

This patch makes additions to the `BlockArgOpenMPOpInterface` to
simplify its use by letting it handle the matching between operands and
their associated entry block arguments. Most significantly, the
following is now possible:

```c++
SmallVector<std::pair<Value, BlockArgument>> pairs;
cast<BlockArgOpenMPOpInterface>(op).getBlockArgsPairs(pairs);
for (auto [var, arg] : pairs) {
  // var points to the operand (outside value) and arg points to the entry
  // block argument associated to that value.
}
```

This is achieved by making the interface define and use `getXyzVars()`
methods, which by default return empty `OperandRange`s and are overriden
by getters automatically produced for the `Variadic<...> $xyz_vars`
tablegen argument of the corresponding clause. These definitions can
then be simplified, since they no longer need to manually define
`numXyzBlockArgs` functions as a result.

A side-effect of this is that all ops implementing this interface will
now publicly define `getXyzVars()` functions for all entry block
argument-generating clauses, even if they don't actually accept all
clauses. However, these would just return empty ranges, so it shouldn't
cause issues.

This change uncovered some incorrect definitions of class declarations
related to the `ReductionClauseInterface`, and the `OpenMP_DetachClause`
incorrectly implementing the `BlockArgOpenMPOpInterface`, so these
issues are also addressed.

0 files changed, 0 insertions, 0 deletions