Omitting configChanges in AndroidManifest.xml breaks split-screen on Android 11

### Issue description
The ExoPlayer demo app in its AndroidManifest.xml uses the attribute
`android:configChanges="keyboard|keyboardHidden|orientation|screenSize|screenLayout|smallestScreenSize|uiMode"`
for its PlayerActivity. But in my app I can't use that attribute. Not having that attribute is fine on Android 10 and below, but I noticed on Android 11, not having that attribute becomes a problem with split screen (and likely PiP, too). Going into split-screen mode while a video is playing and adjusting the split-screen slider, without that AndroidManifest.xml attribute, will make the phone not have a good time. This might be an issue specific to Android 11 but I figured I'd report it here.

### Reproduction steps
* Checkout the tip of the ExoPlayer release branch (the commit I used to repro this is 59b34ede6165d029d86a677fea73a5dd0dd55c74).
* Open the demo app's AndroidManifest.xml and remove this line entirely for the PlayerActivity node:
`android:configChanges="keyboard|keyboardHidden|orientation|screenSize|screenLayout|smallestScreenSize|uiMode"`
* Load up the ExoPlayer demo app on an Android 11 device or emulator.
* Open any video in the demo app.
* Enter split-screen mode and open any other app to be the bottom half of the screen.
* Adjust the split-screen slider.

Expected:
Video gracefully adjusts to the new screen size.

Actual:
Video struggles to adjust to the new screen size.

### Link to test content
https://streamable.com/yanb66

### A full bug report captured from the device
I can email this if needed/wanted.

### Version of ExoPlayer being used
2.12.1, but also affects 2.9.x and likely any other version.

### Device(s) and version(s) of Android being used
Google Pixel 3XL running Android 11
Android Emulator running Android 11