This is one step in the process of removing calls to
Dependency.get(MAIN_HANDLER) and Dependency.get(BG_HANDLER).
Bug: 144503618
Test: atest SystemUITests
Change-Id: Ifbd49efcfe1eaf8af355e6dde4c70bb26c823cd2
This change includes a refactoring to extract static methods from
PreviewInflater into a seperate class to allow for easier testing.
This allows tests to bypas interaction with package manager.
Test: atest SystemUITests
Change-Id: I3211395e7eb78351106cabd8c473f11f06bb0f97