Splits up the flag.

We need two flags:
1. Whether the interactor and repository depend on the controller (which
   is what is being checked by the logic in the CLs in this chain).
   Currently true, can be set to false once we finish removing the
   controller dependency from the interactor and repository.
2. Whether the controller depends on the interactor (currently false,
   cannot be turned on until after the previous flag is eliminated).

This way, we can roll out the logic that severs the dependency on the
controller in repo and interactors without touching legacy code which
still wants to depend on the old controller (extensions of the
BaseUserSwitcherAdapter class do this - a next step would be to replace
those with adapters that can deal with the new data schema).

Bug: 246631653
Test: manually verified
the operations of the full-screen user switcher, the smaller dialog, the
footer in quick settings, and the dropdown switcher on the lock-screen
bouncer.

Change-Id: I8b7ba0aa043aab39266e1e8fbde69697ddf235d0