Making multiuser button work in collapsed QS in split shade

The issue was caused by MultiUserSwitchController always having reference and acting upon multiuser button in expanded QS - that's a different button than collapsed QS.
That reference was provided by dagger and while this issue could be fixed in dagger, that would require providing separate multiuser button and separate MultiUserSwitchController. That would require adding qualifier like @Named in multiple places (both providers and receivers) so seems like too much boilerplate (or opportunity for separate module?) and I went with adding factory for MultiUserSwitchController.

Another issue is MultiUserSwitchController opening multiuser detail always in expanded QS - collapsed QS currently doesn't support opening detail view. Looks like that requires non-trivial code changes, so for now I did it in a hacky way - forcing panel to expand and only then showing multiuser detail (as seen in QSPanelController). I think this hacky way is better than having non-functioning button.

Fixes: 196805122
Test: enable multiuser support -> expand split shade (but not expand QS)
-> click on multiuser button -> multiuser panel should open within QS

Change-Id: I76c9bb77c870b8a1a4e25221c63821786057d7f2