[Important] Hugely simplify GameWindow and rendering

[soywiz]

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Right now GameWindow and rendering is super complicated on the korgw side.

We should simplificate it as much as possible, specially now that we have less targets.

On JS?

• setInterval(60ms): update
• requestAnimationFrame: render

On JVM / Android / Native:

• Thread handling the event loop with a timer every 60 fps: so we have consisent updating. In that thread we don't sleep while we are handling events. Updating the game grabs a lock. After updating if something change, we request a frame update. We can prepare a frame on this thread in a renderbuffer when required.
• On the UI thread, handle frame render requests and just blit the generated renderbuffer in the current frame, do vsync here. Handle also events here. We should either create a shared opengl context, or use a locking mechanism to grab the opengl context.

This should also avoid I/O delays because events are only handled in the event loop and right now that event loop is in a thread that is sleeping on vsync. This should alos fix flickering on windows JVM When not rendering in continuous mode.

This is a long-standing issue, so this task is important. It should also make the code more mainteintable for the long run.

Might worth exploring and create a new simpler API, and then migrate to the old one once we get it right on all the targets.