Merge Input and RequestRedraw events

[Sharktheone]

In #733 there is a channel with events. Ideally we should get all events in the buffer and then

1. Prioritize small events that just change parameters (InputEvent::MouseMove and so on) and afterward execute a potential RequestRedraw event
2. Merge multiple events, when we have multiple
   • MouseMove events, we should drop all events except the last.
   • MouseScroll events, we should collect up all of them and add up the deltas
   • RequestRedraw events, we should only redraw once

This should improve the general responsiveness of the engine because when you use your mouse and the engine can't keep up it will try to always stay most up to date rather than rendering all frames in between the last render and now.