MainSwitchBar is a view widget in activity layout stick to the top of
screen UI. There is no corresponding Preference in the preference
screen. For Catalyst support, introduce an invisible Preference object
to manipulate with MainSwitchBar, so that the binding mechanism is
still working on top of this abstraction.
Bug: 332201912
Flag: EXEMPT new class
Test: manual
Change-Id: If50932a443c1ed3ac04d3ea2e3273724d750297d
