[mlir][Linalg] Expose vectorization precondition check as a utility function.

This patch exposes the method to check if an op can be vectorized or
not for downstream uses. Also adds a check to mark elementwise operations
that have non-vectorizable ops (like `tensor.extract`) as non vectorizable.

Reviewed By: nicolasvasilache, dcaballe, ThomasRaoux

Differential Revision: https://reviews.llvm.org/D135201