[mlir][linalg] Add vectorization for element-wise linalg ops

Add support for vectorization for linalg.generic representing element-wise ops.
Those are converted to transfer_read + vector ops + transfer_write.
Also re-organize the vectorization tests to be together.

Implementation derived from the work of @burmako, @agrue and
@fedelebron.

Differential Revision: https://reviews.llvm.org/D92540