Demarcate cached sets in composition summary

Previously, the composition summary indicated that HWC was compositing
more layers than it actually was.

Example when youtube video open and playing in a free form window
Before: bbrrrRrbbb
After: [b:brr]r[R:rbbb]
So there are 2 cached sets and 1 uncached set. One cached set and one uncached layer is composited by HWC, the other cached set is composed by the GPU.


Bug: 391428079
Flag: EXEMPT log only update
Test: Capture perfetto trace and confirm layers are skipped and overridden as expected

Change-Id: I4ffda43f5248ef8bb690cdaca0eeca7ffac3d997