Add new API windowSplashScreenBehavior for declare splash screen style

Add new API windowSplashScreenBehavior, app can use this API to
declare that this app would prefers to show icon-style splash screen,
and this attribute would takes effect if the launching activity did
not start the activity with SPLASH_SCREEN_STYLE_EMPTY.

Bug: 205907456
Test: atest SplashscreenTests
Change-Id: I576793ec43e704f35ad611c71e250a0e2b080cf1