Add a new abstract class MagnificationFeaturePreferenceController
that extends TogglePreferenceController, to wrap inSetupWizard
setter/getter. Then for magnification feature preference controllers
like alwaysOn or followTyping, they can just check isInSetupWizard to
decide whether hiding in setup wizard.
Besides, in ToggleScreenMagnificationPreferenceFragment we cache a flag
mInSetupWizard when fragment created, so we can pass the info to the
preferece controllers when creating them.
Bug: 340721852
Flag: NONE
Test: build pass
Change-Id: I05c59a766219862117d2a6ede775d68a4c3dedac
