Switch Android port back to winit as well

[wusyong]

Is your feature request related to a problem? Please describe.
Our current implementation is quite different than winit before because winit creates NativeActivity for its application and it's limited when it wants to use several Android API. So we just implement our own custom Activity and bind functions ourselves. This of course creates a workload to maintain android port ourselves.

Describe the solution you'd like
Since winit now adopts android-activity, we can consider switching back to it. android-activity supports another GameActivity which basically inherits AppCompatActivity. We can inherit GameActivity instead in our custom Activity, while keeping binding functions through tao-macros.

Describe alternatives you've considered
While this sounds possible, switching back all over again is definitely a huge task and there are still a few uncertainties. We could just still stick to our own implementation.

Would you want to assign yourself to implement this feature?

• Yes
• No

Additional context
Here's the issue in android-activity: rust-mobile/android-activity#57

[amrbashir]

It would be ideal to add just the base AppCompatActivity directly into android-activity crate along with GameActivity and NativeActivity so we use only what we need because sounds to me that GameActivity has extra functionality that we don't need.