protocol/action-binder: draft implementation.
adds a new type for action binder (wayland/wayland-protocols!216)
current implementation provides the wlr_action_binder_v1 struct for compositors to create the binder struct holds a wl_list of binder states, that are created per-client. the state struct holds a wl_list of that clients bindings
it's still missing a clear way to handle conflicting bindings. currently the first successful bind is the one to receive every action
possible policies for this are, imo, first come first server, so only the first client to a specific bind gets it, and subsequent attempts get REJECTED by default or allow multiple binds, sending the action to every client bound.
Signed-off-by: Anna (navi) Figueiredo Gomes navi@vlhl.dev