Update Readback VTS to align with RenderEngine interface change

RenderEngine no longer directly takes in GraphicBuffer objects. Instead,
it takes in ExternalTexture types that manage resources associated with
a GraphicBuffer.

Bug: 180767535
Test: builds
Change-Id: I13904eec491fce223b6178fa5571589b67402865
diff --git a/graphics/composer/2.2/utils/vts/RenderEngineVts.cpp b/graphics/composer/2.2/utils/vts/RenderEngineVts.cpp
index 3becace..f78dda2 100644
--- a/graphics/composer/2.2/utils/vts/RenderEngineVts.cpp
+++ b/graphics/composer/2.2/utils/vts/RenderEngineVts.cpp
@@ -69,7 +69,9 @@
                    [](renderengine::LayerSettings& settings) -> renderengine::LayerSettings* {
                        return &settings;
                    });
-    mRenderEngine->drawLayers(mDisplaySettings, compositionLayerPointers, mGraphicBuffer, true,
+    auto texture = std::make_shared<renderengine::ExternalTexture>(
+            mGraphicBuffer, *mRenderEngine, renderengine::ExternalTexture::Usage::WRITEABLE);
+    mRenderEngine->drawLayers(mDisplaySettings, compositionLayerPointers, texture, true,
                               std::move(bufferFence), &readyFence);
     int fd = readyFence.release();
     if (fd != -1) {