Implement `From<Transform>` for `wl_output::Transform`
Implement `From<Transform>` for `wl_output::Transform`

I'd assume most Wayland consumers probably mostly want to deal with
Smithay's `Transform`, so it's nice to keep that type consistent in
consumer crates and then have it converted to the protocol's types on
demand.

I've refrained from making changes to the `change_current_state` method
in this patch to keep the patch as uncontroversial as possible, but
changing the parameters to `impl Into<Option<T>>` for at least the
transform of that method similar to how the Size/Point types are
implemented would probably help downstream.

Smithay/smithay,Smithay/smithay,Smithay/smithay,Smithay/smithay