CE: Snapshot layer metadata

Adds LayerMetadata to LayerSnapshots. LayerMetadata is only populated
when CE enables the new feature flag and the feature flag will only be
enabled in ARC++'s CE.

This change is necessary to split LayerFE from the Layer class as
ARC++'s LayerFE subclass accesses LayerMetadata.

Bug: 238781169
Test: go/wm-smoke
Test: presubmit

Change-Id: Iae405707897eedf5af9025fe628c1cd60b596e10
diff --git a/services/surfaceflinger/tests/unittests/Android.bp b/services/surfaceflinger/tests/unittests/Android.bp
index dec14d0..4469df0 100644
--- a/services/surfaceflinger/tests/unittests/Android.bp
+++ b/services/surfaceflinger/tests/unittests/Android.bp
@@ -109,6 +109,7 @@
         "SurfaceFlinger_SetDisplayStateTest.cpp",
         "SurfaceFlinger_SetPowerModeInternalTest.cpp",
         "SurfaceFlinger_SetupNewDisplayDeviceInternalTest.cpp",
+        "SurfaceFlinger_UpdateLayerMetadataSnapshotTest.cpp",
         "SchedulerTest.cpp",
         "SetFrameRateTest.cpp",
         "RefreshRateConfigsTest.cpp",