Let user determines, what events are important for rerendering

[Arash-Rezaie]

When I move mouse even out of the egui window, rerender happens while in version 26.x it was correct. It is a bug, but let user determines what events are important.

[lucasmerlin]

There already is App::raw_input_hook, it'd be nice to maybe extend that to return a boolean/enum and we only repaint if the bool is true or alternatively add a check after raw_input_hook to see if the list of events is now empty we can skip the repaint (if the reason for it was a native event and not e.g. request_repaint)

[barries]

Avoiding mouse movement renders for a GUI that doesn't do hover at all would nice (tm).

As for the raw_input_hook(...) -> bool idea, that sounds great--another similar thing that would also be handy is to be able to do an early return from App::update() because our code uses Context::request_repaint_after() to poll hardware every 100ms and it would be nice to skip the render if hardware hasn't changed state.

For context, the hardware we're polling is a positioning motor in a medical device that spends most of its time sitting still while the surgeon does other things. Or making these schedule renders call raw_input_hook() (or does it already do that? I don't see an obvious Event variant for that, so I assume it doesn't).