Fix a bug in computeTpl() when there are multiple displays.

coveredRegionsAbove computed for one display could affect another
display. We need to extend coveredRegionsAbove to be per-display data so
that each display can be independently calculated.

Bug: 383679189
Flag: EXEMPT bugfix
Test: atest android.view.surfacecontrol.cts.TrustedPresentationListenerTest

Change-Id: I6e9f4fd06a5fcd5b1218c678b43c7f585ccb91e4