useRootNavigator parameter utilized when pushing fullscreen

[Colton127]

By default, betterplayer always uses rootNavigator when pushing full screen. This can cause trouble for those of us with nested routes, as it tends to dispose of previous routes. This simple change utilizes the already supplied "useRootNavigator" parameter during the fullscreen navigator push.

[Colton127]

Updated better_player_controller to always call playerVisibilityChangedBehavior if supplied, regardless of if handleLifecycle is enabled.

[krishaajtak]

@Colton127 can you share which part has the full screen route code?