Remove SystemUIFactory#shouldInitializeComponents

Replaced it with an injectable InitializationChecker class.

This is primarily to remove SystemUIGoogle's reliance on overriding
SystemUIFactory#init.

Bug: 235624311
Test: m SystemUI
Change-Id: I56537764f0f6ea3519211a9403da2bef7c49bc7e
Merged-In: I56537764f0f6ea3519211a9403da2bef7c49bc7e