Since we don't have status bar on external displays, we need to saparate
the logic to make some animations or transitions just work on external
navigation bars. When we set System UI visibility on an external display,
we could make the flag only effect navigation bar. Also, it can simplify
StatusBar code by moving navigation bar related fields into
NavigationBarController.
Test: atest SystemUITests
Bug: 117478341
Change-Id: I1cdf61f6eeb2c377e04a073401efa0cdb45b65cd
10ca70b075