pointer: drop custom enums
Instead, use enums from the Wayland protocol.
We need to decide whether to always borrow enums from the Wayland protocol, or always define our own. This MR does the former for pointer. Notes:
- Technically input devices are part of the backend, they are not protocol implementations.
-
wlr_keyboard
andwlr_output
already use enums from the protocol. - With our own enums we need to convert back and forth. (We can use a simple cast but risk getting out of sync.)
- There will always be some input devices with no protocol equivalent, for instance
wlr_switch
. - Tablet tool/pad doesn't use protocol enums, because the protocol is unstable. A v3 of the protocol would force us to break our API.