[mlir][SCF] Add scf::ForeachThread canonicalization.

This revision adds the necessary plumbing for canonicalizing scf::ForeachThread with the
`AffineOpSCFCanonicalizationPattern`.
In the process the `loopMatcher` helper is updated to take OpFoldResult instead of just values.
This allows composing various scenarios without the need for an artificial builder.

Differential Revision: https://reviews.llvm.org/D128244