Android: Add isGame application attribute, default to true

[akien-mga]

It can be turned off in the export preset with package/classify_as_game.

Upstream definition: https://developer.android.com/guide/topics/manifest/application-element#isGame

android:isGame

Whether or not the application is a game. The system may group together
applications classifed as games or display them separately from other
applications.

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Supersedes #48547.

needs testing as I haven't tested this code yet, just wrote it by analogy with the allowBackup attribute.

[akien-mga]

Tested with the prebuilt APK workflow and it works fine.

However with custom build, it fails with:

Execution failed for task ':processDebugMainManifest'.
> Manifest merger failed : Attribute application@isGame value=(false) from AndroidManifest.xml:23:9-30
  	is also present at AndroidManifest.xml:23:9-30 value=(true).
  	Suggestion: add 'tools:replace="android:isGame"' to <application> element at AndroidManifest.xml:16:5-25:19 to override.

I see that the tools:replace trick is used for android:screenOrientation in activity, but I'm puzzled that android:allowBackup seems to work fine with the exact same code I'm using here for android:isGame.

[akien-mga]

but I'm puzzled that android:allowBackup seems to work fine with the exact same code I'm using here for android:isGame.

Actually no, it's a pre-existing bug, it's just that nobody ever seems to set allowBackup to true for custom builds :)

Execution failed for task ':processDebugMainManifest'.
> Manifest merger failed : Attribute application@allowBackup value=(true) from AndroidManifest.xml:21:9-36
  	is also present at AndroidManifest.xml:21:9-36 value=(false).
  	Suggestion: add 'tools:replace="android:allowBackup"' to <application> element at AndroidManifest.xml:16:5-25:19 to override.

[akien-mga]

Fixed the issues with custom builds, and I've tested a number of combinations successfully (prebuilt APK with and without isGame, custom build AAB with and without isGame and allowBackup).

[akien-mga]

Cherry-picked for 3.4.