Refactor creation of normal dependency records when creating extension

When creating an extension, the same type of dependency is used when
registering a dependency to a schema and required extensions.  This
improves the code so as those dependencies are not recorded one-by-one,
but grouped together.  Note that this has as side effect to remove
duplicate dependency entries, even if it should not happen in practice
as extensions listed as required in a control file should be listed only
once.

Extracted from a larger patch by the same author.

Author: Daniel Dustafsson
Discussion: https://postgr.es/m/20200629065535.GA183079@paquier.xyz

src/backend/commands/extension.c

@@ -1783,6 +1783,7 @@ InsertExtensionTuple(const char *extName, Oid extOwner,
 	HeapTuple	tuple;
 	ObjectAddress myself;
 	ObjectAddress nsp;
+	ObjectAddresses *refobjs;
 	ListCell   *lc;
 
 	/*
@@ -1825,27 +1826,26 @@ InsertExtensionTuple(const char *extName, Oid extOwner,
 	 */
 	recordDependencyOnOwner(ExtensionRelationId, extensionOid, extOwner);
 
-	myself.classId = ExtensionRelationId;
-	myself.objectId = extensionOid;
-	myself.objectSubId = 0;
+	refobjs = new_object_addresses();
 
-	nsp.classId = NamespaceRelationId;
-	nsp.objectId = schemaOid;
-	nsp.objectSubId = 0;
+	ObjectAddressSet(myself, ExtensionRelationId, extensionOid);
 
-	recordDependencyOn(&myself, &nsp, DEPENDENCY_NORMAL);
+	ObjectAddressSet(nsp, NamespaceRelationId, schemaOid);
+	add_exact_object_address(&nsp, refobjs);
 
 	foreach(lc, requiredExtensions)
 	{
 		Oid			reqext = lfirst_oid(lc);
 		ObjectAddress otherext;
 
-		otherext.classId = ExtensionRelationId;
-		otherext.objectId = reqext;
-		otherext.objectSubId = 0;
-
-		recordDependencyOn(&myself, &otherext, DEPENDENCY_NORMAL);
+		ObjectAddressSet(otherext, ExtensionRelationId, reqext);
+		add_exact_object_address(&otherext, refobjs);
 	}
+
+	/* Record all of them (this includes duplicate elimination) */
+	record_object_address_dependencies(&myself, refobjs, DEPENDENCY_NORMAL);
+	free_object_addresses(refobjs);
+
 	/* Post creation hook for new extension */
 	InvokeObjectPostCreateHook(ExtensionRelationId, extensionOid, 0);