LightBarController updates button tint on navigation mode change

This ensures lighting changes made while in gesture navigation
are properly applied when switching to 3-button navigation.

Flag: android.view.accessibility.light_bar_update_button_tint_on_nav_mode_change
Bug: 387395420
Test: atest LightBarControllerTest
Change-Id: I9a89079a4ec9195aa826c5728dbd6d1449ba5304