[mlir][TilingInterface] Enabling tiling `tensor.pad` using `TilingInterface`.

Update the implementation of `TilingInterface` for `tensor.pad`
operations to allow tiling the op using the existing patterns for the
interface. Verify that tests that pass with existing pad tiling
patterns producer the same results through TilingInterface patterns.

Reviewed By: antiagainst

Differential Revision: https://reviews.llvm.org/D132720