[PhaseOrdering] add shuffle tests based on D40633; NFC

We got some of the potential optimizations with D76727 and D76844.
There are 2 likely enhancements that we could add to -vector-combine
to get most of the remaining cases:
1. Allow bitcasted shuffle mask narrowing (widen the elements).
2. Combine shuffle-of-shuffle into a single shuffle.

This is already partly handled by the x86 backend, but the
tests here show that we still miss some of the potential
combines.