SF: Fix dumpVisibleLayersProtoInfo

dumpVisibleLayersProtoInfo was indexing into mDisplays using the HWC
display ID, which is incorrect if the primary display does not map to
the first element of the KeyedVector.

Bug: 74619554
Test: dumpsys SurfaceFlinger --dump-layer-stats
Change-Id: I5255822bb088967a64c646899fc9569a20848641