[mlir][bufferize] Deallocate returned buffers with `BufferDeallocation`

New buffer allocations can now be returned/yielded from blocks with `allow-return-allocs`. One-Shot Bufferize deallocates all buffers at the end of the block. If this is not possible (because the buffer escapes the block), this is now done by the existing BufferDeallocation pass.

Differential Revision: https://reviews.llvm.org/D121527