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/Android.bp b/services/surfaceflinger/Android.bp
index 8a76d7c..67a226e 100644
--- a/services/surfaceflinger/Android.bp
+++ b/services/surfaceflinger/Android.bp
@@ -163,6 +163,7 @@
         "HwcSlotGenerator.cpp",
         "WindowInfosListenerInvoker.cpp",
         "Layer.cpp",
+        "LayerFE.cpp",
         "LayerProtoHelper.cpp",
         "LayerRenderArea.cpp",
         "LayerVector.cpp",