Extend settings panel under navigation bar

The panel used to sit above the navigation bar. Now it extends down all
the way to the edge of the screen.

Bug: b/250484565
Test: make ROBOTEST_FILTER=SettingsPanelActivityTest RunSettingsRoboTests -j40
Test: Manual. When volume panel is opened, verify that it extends all
the way to the bottom of the window, instead of sitting on navigation
bar. Panel can be opened with:
adb shell am start -a android.settings.panel.action.VOLUME
Substitute VOLUME with NFC and WIFI for the other settings panels.

Change-Id: Ibae5d3602231e2309b5ff847c630a1f8c82ea355