SF: Virtual display ID conflict resolution

Currently, there are no safeguards against duplicate display IDs when
creating displays of any kind (physical or virtual). In rare cases where
duplicates occur, they cause critical failures in display management.

This patch introduces:
1. Logic around virtual display creation to keep generating virtual
   display IDs until there is no collision with existing displays.
2. Avoidance logic and checks against display ID duplicates in
   SurfaceFlinger around creation of VirtualDisplaySnapshot.
3. Robust testing of SurfaceFlinger::acquireVirtualDisplay.

Flag: com.android.graphics.surfaceflinger.flags.stable_edid_ids
Bug: 421463837
Test: DisplayTransactionCommitTest#acquire*VirtualDisplayId*
Change-Id: Ib666e4ddc5ce10cd7ee624ccd10c321d5c88d932