Provide access to primary output metadata in ActionExecutedEvent.

PiperOrigin-RevId: 434562647

Author: janakdr

src/main/java/com/google/devtools/build/lib/actions/ActionExecutedEvent.java

@@ -120,6 +120,11 @@ public ImmutableList<MetadataLog> getActionMetadataLogs() {
     return actionMetadataLogs;
   }
 
+  @Nullable
+  public FileArtifactValue getPrimaryOutputMetadata() {
+    return primaryOutputMetadata;
+  }
+
   @Override
   public BuildEventId getEventId() {
     if (action.getOwner() == null) {