Add config to disable using the appIcon for splash screens

Splash screens by default show the appIcon in the splash screen.
However, on some form factors (e.g. TV) apps have widely implemented their
own splash screen, which is drawn as soon as the app is ready to draw.
If for such apps Android also puts the appIcon in the system splash screen,
this creates a duplicated splash screen experience, where the two
splash screens are completely different, which doesn't look good.

Therefore, in this CL we want to disable the behaviour of using the
appIcon in the splash screen as a fallback option. Instead, if the app
has specified a splash screen specific icon (via the attribute
windowSplashScreenAnimatedIcon), that is a signal that the app wants to
use the system splash screen and has taken care to remove the duplicated
splash screen experience.

This CL introduces a config_canUseAppIconForSplashScreen and sets it to
true by default and to false for TV. The CL doesn't change the behaviour
on non-TV devices.

Bug: 296354973
Test: atest StartingWindowControllerTests
Change-Id: Ifa432b178ea0be311e9b9aa4c9ab3be3b329c967