SF: Add new fields to transactions proto

- track layer handle removal so layer lifecycle
  can be recreated accurately when rebuilding layer
  state
- track buffer format since it affects opacity
- track transaction ids to track transactions
  across the system
- also fixes relative z tracking

Test: atest TransactionProtoParserTest
Bug: 200284593
Change-Id: I037e40219f9fee8957051352beeba88681b8cf43
diff --git a/services/surfaceflinger/BufferLayer.cpp b/services/surfaceflinger/BufferLayer.cpp
index 649138a..e797b5d 100644
--- a/services/surfaceflinger/BufferLayer.cpp
+++ b/services/surfaceflinger/BufferLayer.cpp
@@ -820,6 +820,10 @@
     return isFixedSize();
 }
 
+const std::shared_ptr<renderengine::ExternalTexture>& BufferLayer::getExternalTexture() const {
+    return mBufferInfo.mBuffer;
+}
+
 } // namespace android
 
 #if defined(__gl_h_)