Remove unused code

* Remove BufferLayer::bindTextureImage
* Remove RenderEngine::bindExternalTextureBuffer. In particular, this
function was legacy back from 2012 around when SurfaceTexture was forked
into SurfaceFlinger. By now there's been some architectural changes,
including Treble enforcement of a process boundary between SF and HWC,
meaning that the "implicit synchronization" no longer really makes
sense to enforce.

Bug: 168553972
Test: builds
Test: Cuttlefish boots, can interact without visual artifacts.
Change-Id: I259160ccc6cc02fe3ac0d9b5edc4c1c72d3d582f
diff --git a/libs/renderengine/gl/GLESRenderEngine.h b/libs/renderengine/gl/GLESRenderEngine.h
index 8f0df2c..c72b7f9 100644
--- a/libs/renderengine/gl/GLESRenderEngine.h
+++ b/libs/renderengine/gl/GLESRenderEngine.h
@@ -60,8 +60,6 @@
     void primeCache() const override;
     void genTextures(size_t count, uint32_t* names) override;
     void deleteTextures(size_t count, uint32_t const* names) override;
-    status_t bindExternalTextureBuffer(uint32_t texName, const sp<GraphicBuffer>& buffer,
-                                       const sp<Fence>& fence) EXCLUDES(mRenderingMutex);
     void cacheExternalTextureBuffer(const sp<GraphicBuffer>& buffer) EXCLUDES(mRenderingMutex);
     void unbindExternalTextureBuffer(uint64_t bufferId) EXCLUDES(mRenderingMutex);
 
@@ -135,6 +133,8 @@
     status_t bindFrameBuffer(Framebuffer* framebuffer);
     void unbindFrameBuffer(Framebuffer* framebuffer);
     void bindExternalTextureImage(uint32_t texName, const Image& image);
+    void bindExternalTextureBuffer(uint32_t texName, const sp<GraphicBuffer>& buffer,
+                                   const sp<Fence>& fence) EXCLUDES(mRenderingMutex);
     void cleanFramebufferCache() EXCLUDES(mFramebufferImageCacheMutex) override;
 
     // A data space is considered HDR data space if it has BT2020 color space