In 3-button landscape/seascape, override nav insets to always present

- In 3-button landscape/seascape, Launcher should always have nav insets regardless if it's initiated from fullscreen apps
- This avoid inset to change mid-way during app->overview transition via recents button
- This bug doesn't happen in portrait because bottomNav is always overriden in WindowManagerProxy, we're now applying the same fix in landscape/seascape

Test: Recents button from fullscreen app in 3-button landscape/seascape, and launch adjacent fullscreen app in Overview
Test: Homescreen and widget picker in 3-button landscape/seascape
Fix: 316085856
Flag: None
Change-Id: Ia4ae7948fe794b71c49f89c43dd2d1d14031abb9