Revert "Revert "Add ExternalTexture class into RenderEngine inte..."

Revert submission 14199598-revert-14086921-renderengine-external-tex-QJNBWQMQEU

Reason for revert: Prepare for relanding
Reverted Changes:
I01e65a7f4:Revert "Update WaylandRenderSurface to accomodate ...
I7d58118c1:Revert "Update Readback VTS to align with RenderEn...
I1501890f4:Revert "Add ExternalTexture class into RenderEngin...

Added the following fixes:
1. CachedSet renders to intermediate texture variable rather than
mTexture directly, since mTexture is not guaranteed to be nonnull.
2. Add null check when setting new buffer in BLAST.

Bug: 185524947
Bug: 180767535
Test: builds, boots
Test: librenderengine_test
Change-Id: I52ea82e24336b496d996bbe3e445db0affe1abb8
diff --git a/services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp b/services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp
index f640f85..9ca8914 100644
--- a/services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp
+++ b/services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp
@@ -537,7 +537,7 @@
     sp<GraphicBuffer> buffer = outputIndependentState.buffer;
     sp<Fence> acquireFence = outputIndependentState.acquireFence;
     if (getState().overrideInfo.buffer != nullptr) {
-        buffer = getState().overrideInfo.buffer;
+        buffer = getState().overrideInfo.buffer->getBuffer();
         acquireFence = getState().overrideInfo.acquireFence;
     }
 
@@ -699,7 +699,7 @@
     settings.geometry = renderengine::Geometry{
             .boundaries = boundaries.toFloatRect(),
     };
-    settings.bufferId = getState().overrideInfo.buffer->getId();
+    settings.bufferId = getState().overrideInfo.buffer->getBuffer()->getId();
     settings.source = renderengine::PixelSource{
             .buffer = renderengine::Buffer{
                     .buffer = getState().overrideInfo.buffer,