Add detailed Skia traces sysprop to RenderEngine.

BUG:180767647
Test: setprop, force client composition, perfetto trace

1. `adb shell setprop debug.renderengine.skia_atrace_enabled 1`
2. `adb shell stop && adb shell start`
3. Force client composition:
   `adb shell service call SurfaceFlinger 1008 i32 1`
   (`adb shell dumpsys SurfaceFlinger | grep -A 30 "HWC layers"` can
   be used to check layers are "CLIENT" instead of "DEVICE".)
4. Perfetto script to trace.
5. See skia traces e.g. `grsurfacedrawcontext` in surfaceflinger
RenderEngine process.

Change-Id: I0612e3df82de08ab6a754b4f60d09057d335b1b1