[mlir][bufferization] `MaterializeInDestinationOp`: Support memref destinations (#68074)

Extend `bufferization.materialize_in_destination` to support memref
destinations. This op can now be used to indicate that a tensor
computation should materialize in a given buffer (that may have been
allocated by another component/runtime). The op still participates in
"empty tensor elimination".

Example:
```mlir
func.func @test(%out: memref<10xf32>) {
  %t = tensor.empty() : tensor<10xf32>
  %c = linalg.generic ... outs(%t: tensor<10xf32>) -> tensor<10xf32>
  bufferization.materialize_in_destination %c in restrict writable %out : (tensor<10xf32>, memref<10xf32>) -> ()
  return
}
```
After "empty tensor elimination", the above IR can bufferize without an
allocation:
```mlir
func.func @test(%out: memref<10xf32>) {
  linalg.generic ... outs(%out: memref<10xf32>)
  return
}
```

This change also clarifies the meaning of the `restrict` unit attribute
on `bufferization.to_tensor` ops.