Switch to GameActivity

[jb55]

This is needed for

• Android softkeyboard support #199

Follow up tasks:

• Show system bar above application #172

egui projects

Here's an egui project that has GameActivity implemented:

• https://github.com/podusowski/walkers/tree/main/demo_android

We can use this as a guide

Alternative

Since this is kind of a pain in the ass and requires a bunch of things, we should take a look at:

• Try android keyboard via WindowInsetsController #674

to see if we can get it working in NativeActivity