[mlir][VectorOps] Expose SuperVectorizer as a utility

This patch refactors a small part of the Super Vectorizer code to
a utility so that it can be used independently from the pass. This
aligns vectorization with other utilities that we already have for loop
transformations, such as fusion, interchange, tiling, etc.

Reviewed By: nicolasvasilache

Differential Revision: https://reviews.llvm.org/D84289