Restrict the GameManagerService's getGameMode() and setGameMode() functionality to only work with applications that are categorized as games. Bug: b/178860939 Test: atest GameManagerTests Test: atest GameManagerServiceTests Test: atest GameManagerServiceSettingsTests Test: atest CtsGameManagerTestCases Change-Id: Iaf42b995db3ef2a4040a5bf46dc327a952d4aa88