Move bar panels above the system bar window layer.

We use the new TYPE_NAVIGATION_BAR_PANEL for this instead of
TYPE_STATUS_BAR_PANEL (which is indeed above the status bar,
but far below the navigation bar, which is the window type
used for the system bar now.)

Bug: 6319161 (ticker underneath system bar)
Bug: 6437342 (missing clear all button on system bar)
Change-Id: Ib58c0003c4c81db64edca2c1bbc2d764c3237ed0