[mlir][vector] Adds pattern rewrite for maskable Ops (#83827)

Adds a generic pattern rewrite for maskable Ops, `MaskableOpRewritePattern`,
that will work for both masked and un-masked cases, e.g. for both:

* `vector.mask {vector.contract}` (masked), and
* `vector.contract` (not masked).

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

Fixes #78787