Separate android initialization from Activity

[isXander]

Separates initialization and JNI hooks from SDLActivity, into a separate class SDLActivityComponent. SDLActivity uses this to apply the functionality onto the activity.

Description

Currently, all SDL initialization on Android is done within an Activity. Whilst this is good for simplicity, it doesn't allow a lot of flexibility for Android apps; some apps' activities may already inherit something else, making it extremely impractical to get SDL to work.
Removing all functionality from the activity into a separate class, SDLActivityComponent, allows developers to compose the SDL glue code into their existing activity. SDLActivity remains, as a simple semi-backwards-compatible way that also demonstrates how to use the new SDLActivityComponent.

Existing Issue(s)

#11890

[VenomousSteam81]

Very cool!

[isXander]

Whilst on the topic of the java library, Android Studio picked up a few errors:

• HIDDeviceBLESteamController.java requires permission android.permission.BLUETOOTH_CONNECT
• HIDDeviceManager.java: mUsbBroadcast is missing RECEIVER_EXPORTED or RECEIVER_NOT_EXPORTED flag for unprotected broadcasts registered for org.libsdl.app.USB_PERMISSION

[isXander]

All relevant test environments are passing now. Failures match base branch.

[isXander]

Ready for review!

[slouken]

Merged, thanks!

[slouken]

This ended up being a major breaking change for activities that inherit from SDLActivity, so we don't want this to go in so close to 3.2.0 release.

Here's a sample of the kinds of things that broke:

error: component has private access in SDLActivity
                component.setWindowStyle( true );

error: method does not override or implement a method from a supertype
error: COMMAND_CHANGE_WINDOW_STYLE has protected access in SDLActivityComponent
    @Override
    protected boolean sendCommand(int command, Object data)
    {       
        if ( command == SDLActivityComponent.COMMAND_CHANGE_WINDOW_STYLE && (Integer)data == 0 )

error: mLayout has protected access in SDLActivityComponent
                SDLActivityComponent.mLayout.addView( m_videoSurface );

[isXander]

Would you accept a second PR that addresses the backwards compatibility more? Providing more overridable methods in SDLActivity to configure the component?

[slouken]

Would you accept a second PR that addresses the backwards compatibility more? Providing more overridable methods in SDLActivity to configure the component?

Sure.