Retrieve a list of composition settings from front end layer

Replace prepareClientComposition and prepareShadowClientComposition
calls with one that provides a list of composition settings in z-order
to handle layers that renders shadows wihtout any content.
If the EffectLayer is called with an invalid color, skip the color fill.

Test: atest libcompositionengine_test
Test: LayerTransactionTest.SetFlagsSecureEUidSystem
Test: go/wm-smoke
Change-Id: Iad16931341fc2e58247f4439a322c0ad1e8750f8
diff --git a/services/surfaceflinger/BufferLayer.h b/services/surfaceflinger/BufferLayer.h
index 4085b52..0487e38 100644
--- a/services/surfaceflinger/BufferLayer.h
+++ b/services/surfaceflinger/BufferLayer.h
@@ -173,14 +173,15 @@
     BufferInfo mBufferInfo;
     virtual void gatherBufferInfo() = 0;
 
+    std::optional<compositionengine::LayerFE::LayerSettings> prepareClientComposition(
+            compositionengine::LayerFE::ClientCompositionTargetSettings&) override;
+
     /*
      * compositionengine::LayerFE overrides
      */
     const compositionengine::LayerFECompositionState* getCompositionState() const override;
     bool onPreComposition(nsecs_t) override;
     void preparePerFrameCompositionState() override;
-    std::optional<compositionengine::LayerFE::LayerSettings> prepareClientComposition(
-            compositionengine::LayerFE::ClientCompositionTargetSettings&) override;
 
     // Loads the corresponding system property once per process
     static bool latchUnsignaledBuffers();