[MLIR] Update/fix memref region computation for affine.parallel ops

When the affine.parallel op was introduced, affine utilities weren't
extended to handle it. Extending these is straightforward and natural
given that addAffineParallelOpDomain has also been added.
Update/complete memref region compute to account for affine.parallel
ops. Handle failure cleanly.

Add and expose utilities missing for affine.parallel to be consistent
with affine.for.

All of these allow various affine passes to work with a combination of
affine.parallel and affine.for ops.

Differential Revision: https://reviews.llvm.org/D145669