Ensure FLAG_IN_APP is correctly set after launcher-restart.

This is a follow-up to ag/21699905, which caused the nav-bar to be visible after a device-restart alongside the hotseat, until an app was launched.

Currently, when restarting launcher (for example a device restart), there is no guarantee when the SysUI flags are received for the first time. The current init-codepath  expects the launcher to be fully initialized at the time. From there, only deltas are processed:
- during the initial resume, launcher is not considered active because the screen is still off
- the SCREEN_ON event itself is not processed to update the FLAG_IN_APP

Before: http://shortn/_MGQjGFRIaB
After: http://shortn/_awiv2CxFn9

Bug: 261418621
Test: manual (http://shortn/_ty9EDuLM97), tapl
Change-Id: Ie3b3ba1ebe249efe8fc43850052bc9956cafcd24