Fixup a few flexiglass lockscreen layout issues

Remaining visual bugs have been forked into their own issues so that we
can better track how much work is left to be completed.

Bug: 434918217
Bug: 432451019
Test: Manually checked bug reproductions
Flag: com.android.systemui.scene_container
Change-Id: I6c3233bbfd932ff16867d14d4925c2b31d3e7ca8