Accounting for user switcher on split shade lock screen

Adjusting KeyguardClockPositionAlgorithm so it properly positions elements when user switcher is visible - moving notifications down and keeping clock at the same place.
Also actually passing height of old user switcher (compared to new QS user switcher) to the algorithm.

Bug: 210121179
Test: KeyguardClockPositionAlgorithmTest + manual
Change-Id: I76a84b4f2eca76981cc69a7a1163709a7e8d516c