SF caching: Skip BT601_625 layers for caching and hole-punch

Bug: 188428469
Test: manual
Test: libcompositionengine_test

Such layers render differently on the GPU vs the DPU, so avoid caching
them and rendering them with a hole-punch. Doing either one would result
in a color shift when moving in or out of caching.

Remove isHdr from LayerState. Consolidate its check at its only
call-site, inside CachedSet, where we decide whether to skip
a layer.

Change-Id: I2931cd08d1eca728adefb2e73b6e3e0bd2e67b24