New logic for calculating qsVisible

This logic has been wrong for a long, long time, and it has remained
this way mostly out of caution. Now that we have shifted to flag
based development, we can put this change into the codebase safely
and find out whether it improves matters or breaks things.

Bug: 412476562
Flag: com.android.systemui.shade_qsvisible_logic
Test: ran affected tests; manually verified
Change-Id: I6abb5b4a793ed77d5b4d6bb59bc77da1f7807ad5