[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/DisplayDevice.h b/services/surfaceflinger/DisplayDevice.h
index ddb09c5..912deef 100644
--- a/services/surfaceflinger/DisplayDevice.h
+++ b/services/surfaceflinger/DisplayDevice.h
@@ -84,7 +84,7 @@
             const wp<IBinder>& displayToken,
             const sp<ANativeWindow>& nativeWindow,
             const sp<DisplaySurface>& displaySurface,
-            std::unique_ptr<RE::Surface> renderSurface,
+            std::unique_ptr<renderengine::Surface> renderSurface,
             int displayWidth,
             int displayHeight,
             bool hasWideColorGamut,
@@ -231,7 +231,7 @@
     sp<ANativeWindow> mNativeWindow;
     sp<DisplaySurface> mDisplaySurface;
 
-    std::unique_ptr<RE::Surface> mSurface;
+    std::unique_ptr<renderengine::Surface> mSurface;
     int             mDisplayWidth;
     int             mDisplayHeight;
     mutable uint32_t mPageFlipCount;