Enable applications to report whether they handled an input event #31
Description
When running with NativeActivity / InputQueue then when we "finish" the processing of an event we can tell the input queue if the application handled the event and if not it's possible that there will be some fallback / default handling.
Currently we're reporting that the event was always handled so there will never be any fallback, since this was a simple way to have consistency with GameActivity.
We should make it possible to support fall backs via an InputQueue or potentially support fall backs with GameActivity in the future too.
This was highlighted during the review for this winit backend PR: rust-windowing/winit#2444 where it was also noted that winit may want expose the same notion to allow fall backs for volume controls.