SF: Remove *DisplayId::tryCast usage from VirtualDisplaySurface

Work towards DisplayId opaqueness by eliminating call-sites to APIs that
parse the display ID values directly. One such site is
VirtualDisplaySurface.

Replace all calls to *DisplayId::tryCast with a VirtualDisplayIdVariant
guard.

Flag: com.android.graphics.surfaceflinger.flags.stable_edid_ids
Bug: 390690584
Test: libsurfaceflinger_unittest
Change-Id: I7ae9e838547c31ce09349e15f7d23e99f313646b