[performance improvement] remove duplicate LoadShardList call (#7380)

LoadShardList is called twice, which is not neccessary, and there is no
need to sort the shard placement list since we only want to know the list
length.

src/backend/distributed/metadata/metadata_cache.c

@@ -381,7 +381,7 @@ EnsureModificationsCanRun(void)
 
 
 /*
- * EnsureModificationsCanRunOnRelation firsts calls into EnsureModificationsCanRun() and
+ * EnsureModificationsCanRunOnRelation first calls into EnsureModificationsCanRun() and
  * then does one more additional check. The additional check is to give a proper error
  * message if any relation that is modified is replicated, as replicated tables use
  * 2PC and 2PC cannot happen when recovery is in progress.

src/backend/distributed/utils/colocation_utils.c

@@ -362,10 +362,8 @@ ErrorIfShardPlacementsNotColocated(Oid leftRelationId, Oid rightRelationId)
 									  leftRelationName, rightRelationName)));
 		}
 
-		List *leftPlacementList = ShardPlacementListSortedByWorker(
-			leftShardId);
-		List *rightPlacementList = ShardPlacementListSortedByWorker(
-			rightShardId);
+		List *leftPlacementList = ShardPlacementList(leftShardId);
+		List *rightPlacementList = ShardPlacementList(rightShardId);
 
 		if (list_length(leftPlacementList) != list_length(rightPlacementList))
 		{

src/backend/distributed/utils/shardinterval_utils.c

@@ -470,12 +470,11 @@ SingleReplicatedTable(Oid relationId)
 		return false;
 	}
 
-	List *shardIntervalList = LoadShardList(relationId);
 	uint64 *shardIdPointer = NULL;
-	foreach_ptr(shardIdPointer, shardIntervalList)
+	foreach_ptr(shardIdPointer, shardList)
 	{
 		uint64 shardId = *shardIdPointer;
-		shardPlacementList = ShardPlacementListSortedByWorker(shardId);
+		shardPlacementList = ShardPlacementList(shardId);
 
 		if (list_length(shardPlacementList) != 1)
 		{