Drop phosh private protocol

we don't use it except for rotation which should be done via output-management.

• drop xdg-switcher
• drop rotate-display (!192 (merged))
• drop keyboard_event (upstream replacement?)
• drop thumbnail (upstream replacement?)

we should then bump the protocol version and declare a breaks against older phosh versions in the packaging (since we usually can't remove protocols but since it's private it's o.k.)