[SettingsLib] Add method to allow using a non collapsing toolbar

To enable OEMs to fix the settings toolbar in the collapsed state we add
a method that is overriden by users of the library so that they can
customize collapsibility.

Flag: NONE This change is basically introducing a flag but in a way that
      OEMs can overaly the value. Coupling with another flag will gate
      nothing in droidfood populations.
Test: Overlay the resource in permissions module and observe UI change
Bug: 344908070
Change-Id: I83437376b5f9033b33764c07dde200c2e8369fdf