[MLIR][OpenMP] Improve loop wrapper representation (#97706)

This patch replaces the `SingleBlockImplicitTerminator<"TerminatorOp">`
trait of loop wrapper operations for the `SingleBlock` trait. This
enables a more robust implementation of the
`LoopWrapperInterface::isWrapper()` method, since it does no longer have
to deal with the potentially missing (implicit) terminator.

The `LoopWrapperInterface::isWrapper()` method is also extended to not
identify as wrappers those operations which have a loop wrapper
operation inside that is not taking a wrapper role. This is important
for cases where `omp.parallel` is nested, which can but is not required
to work as a loop wrapper.

Tests are updated to integrate these representation and validation
changes.

0 files changed, 0 insertions, 0 deletions