[mlir][bufferization] Transfer `restrict` during empty tensor elimination (#68729)

Empty tensor elimination is looking for
`bufferization.materialize_in_destination` ops with a `tensor.empty`
source. It replaces the `tensor.empty` with a `bufferization.to_tensor
restrict` of the memref destination. As part of this rewrite, the
`restrict` keyword should be removed, so that no second `to_tensor
restrict` op will be inserted. Such IR would be invalid.
`bufferization.materialize_in_destination` with memref destination and
without the `restrict` attribute are ignored by empty tensor
elimination.

Also relax the verifier of `materialize_in_destination`. The `restrict`
keyword is not generally needed because the op does not expose the
buffer as a tensor.