Report contentInsets only based on what they will be inside apps

This avoids changing them when going from an app to launcher (most obvious when going to overview).

This also allows us to not change insets on apps when opening/closing IME, which reduces potential jumpiness.

Finally, also use this logic for 3P launchers by calling directly from TaskbarDragLayerController instead of TaskbarUIController (which was only overridden by LauncherTaskbarUIController). This fixes some bad issues like sending fullscreen insets when opening a folder from taskbar.

Test: Open Calculator, unstash taskbar, go to overview and ensure no jump as taskbar stashes.
Fixes: 200805319
Change-Id: I4f1cc187398d0051863ff44ea90b7ab9c6aaa8f9