[MLIR][Affine][VectorOps] Vectorize uniform values in SuperVectorizer

This patch adds basic support for vectorization of uniform values to SuperVectorizer.
For now, only invariant values to the target vector loops are considered uniform. This
enables the vectorization of loops that use function arguments and external definitions
to the vector loops. We could extend uniform support in the future if we implement some
kind of divergence analysis algorithm.

Reviewed By: nicolasvasilache, aartbik

Differential Revision: https://reviews.llvm.org/D86756