westoy: Remove MAXIMIZED and FULLSCREEN as separate window types

westoy: Remove MAXIMIZED and FULLSCREEN as separate window types

xdg_shell changes this around so that they are flags on the remote
object itself, not separate surface types. Move to a system where
we calculate the state from the flags ourselves and set the appropriate
wl_shell_surface type.

When we port to xdg_shell, we'll drop these flags and simply sync
on the client.