[RenderEngine] Organize RenderEngine directory.

This patch:
1. adds proper namespace renderengine to all RenderEngine code,
   and namespace gl to all GLES related code
2. creates gl/ directory for GLES backend code
3. Reorder include header files, remove unused header files.

BUG: 112585051
Test: Build, flash, run display validation
Change-Id: I81f0b8831213607cde08562958f7c38ddaf4c9e6
diff --git a/services/surfaceflinger/Layer.h b/services/surfaceflinger/Layer.h
index 604ec65..56261b9 100644
--- a/services/surfaceflinger/Layer.h
+++ b/services/surfaceflinger/Layer.h
@@ -284,7 +284,8 @@
         return getLayerStack() == layerStack && (!mPrimaryDisplayOnly || isPrimaryDisplay);
     }
 
-    void computeGeometry(const RenderArea& renderArea, Mesh& mesh, bool useIdentityTransform) const;
+    void computeGeometry(const RenderArea& renderArea, renderengine::Mesh& mesh,
+                         bool useIdentityTransform) const;
     FloatRect computeBounds(const Region& activeTransparentRegion) const;
     FloatRect computeBounds() const;