SF: Dump CompositionEngine layers and cleanup output

No code was calling compositionengine::Layer::dump. This adds a call,
and cleans up a few odd details about the output so it looks
reasonable.

Test: dumpsys SurfaceFlinger
Bug: 121291683

Change-Id: Iad524ddcd1fe99c0a1670a8ebb045ecbffd5b2eb
diff --git a/services/surfaceflinger/CompositionEngine/src/Output.cpp b/services/surfaceflinger/CompositionEngine/src/Output.cpp
index ad4c7bf..d22bdaf 100644
--- a/services/surfaceflinger/CompositionEngine/src/Output.cpp
+++ b/services/surfaceflinger/CompositionEngine/src/Output.cpp
@@ -147,7 +147,7 @@
         out.append("    No render surface!\n");
     }
 
-    out.append("\n   %d Layers", mOutputLayersOrderedByZ.size());
+    android::base::StringAppendF(&out, "\n   %zu Layers\b", mOutputLayersOrderedByZ.size());
     for (const auto& outputLayer : mOutputLayersOrderedByZ) {
         if (!outputLayer) {
             continue;