[mlir][vector] Add pattern to shuffle bitcast ops

[mlir][vector] Add pattern to shuffle bitcast ops

These patterns move vector.bitcast ops to be before
insert ops or after extract ops where suitable.
With them, bitcast will happen on smaller vectors
and there are more chances to share extract/insert
ops.

Reviewed By: ThomasRaoux

Differential Revision: https://reviews.llvm.org/D96040