[mlir][tensor] Merge consecutive insert_slice/extract_slice ops

Consecutive tensor.insert_slice/tensor.extract_slice can be
created for the case like tiling convolution and then downsizing
2-D convolutions into 1-D ones. It hinders further transformations.
So adding these patterns to clean it up.

Given that bufferization is sensitive and have requirements over
the IR structure (see https://reviews.llvm.org/D132666),
these patterns are put in Transforms/ with separate entry points
for explicit collection.

Reviewed By: ThomasRaoux, mravishankar

Differential Revision: https://reviews.llvm.org/D133871