[mlir][vector] Adds pattern rewrite for maskable Ops

Adds a generic pattern rewrite for maskable Ops that we would like to
work for both masked and un-masked cases, e.g. for both `vector.mask
{vector.contract}` and `vector.contract` (this is a very contrived
example - just to demonstrate the idea).

This helps to reduce code-duplication and standardise how we implement
such patterns.

Fixes #78787

Author: banach-space