Defer loading decoration app icon/name until it's needed

To avoid jank during an app launch, defer loading the app info used in
the veil/handle menu/window header until it's actually about to be
shown.

Bug: 335975211
Test: in perfetto trace - check loadAppInfo trace isn't present during
split launch

Change-Id: I2277a4c5034fdf1ec31bba79091ca89e1f9b090a