core: move wayland event reading to the poll thread plus cleanup

[PaideiaDilemma]

This implements hyprwm/hyprlock#655 but here in xdph.

It might improve the experience on nvidia cards, but unsure if that's really the case.

The second commit does some cleanup regarding timers.
Removes this m_mEventMutex and instead uses a resource specific mutex for the timers.
Also locks the timers mutex when we add a new timer potentially fixing some races.

So far I only tested screensharing.