SF: Split FE and CE

Make LayerFE a standalone class with no links back to Layer. Pass
LayerSnapshot from Layer into LayerFE before CompositionEngine::present
and back after.

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

Change-Id: I5395fb717a931f88e2bf26395acd21e8b308961e
diff --git a/services/surfaceflinger/SurfaceFlingerDefaultFactory.h b/services/surfaceflinger/SurfaceFlingerDefaultFactory.h
index 447a02f..2c6de0e 100644
--- a/services/surfaceflinger/SurfaceFlingerDefaultFactory.h
+++ b/services/surfaceflinger/SurfaceFlingerDefaultFactory.h
@@ -42,6 +42,7 @@
     std::unique_ptr<compositionengine::CompositionEngine> createCompositionEngine() override;
     sp<Layer> createBufferStateLayer(const LayerCreationArgs& args) override;
     sp<Layer> createEffectLayer(const LayerCreationArgs& args) override;
+    sp<LayerFE> createLayerFE(const std::string& layerName) override;
     std::unique_ptr<FrameTracer> createFrameTracer() override;
     std::unique_ptr<frametimeline::FrameTimeline> createFrameTimeline(
             std::shared_ptr<TimeStats> timeStats, pid_t surfaceFlingerPid) override;