[mlir][arith] Add narrowing patterns to commute more vector ops

This commutes the extension (`arith.extsi`, `arith.extui`) over the
following vector ops: `vector.broadcast`, `vector.shape_cast`,
`vector.transpose`, `vector.flat_transpose`.

I focused on these as I saw them getting created by vector unroll
patterns. Maybe except `vector.flat_transpose`.

Reviewed By: antiagainst

Differential Revision: https://reviews.llvm.org/D149534