[mlir][vector][nvgpu] Move MMA contraction preparation to VectorUtils

This pattern is not specific to nvgpu; I intend to use in SPIR-V codegen. `VectorTransforms` seems like a more generally useful place.

In addition:
-  Fix a bug in the second condition (the dimensions were swapped for RHS).
-  Add tests.
-  Add support for externally provided filter functions, similar to other vector transforms.
-  Prefer to transpose before zero/sign-extending inputs.

Reviewed By: ThomasRaoux

Differential Revision: https://reviews.llvm.org/D145638