ttljob: add hint to use PK in delete query

This will help avoid choosing a plan that scans a secondary index, which
can lead to many KV rows being scanned and also lead to contention.

Release note (bug fix): Fixed a bug that could cause DELETE queries sent
by the row-level TTL job to use a secondary index rather than the
primary index to find the rows to delete. This could lead to some DELETE
operations taking a much longer time than they should. This bug was
present since v22.2.0.

pkg/sql/ttl/ttljob/ttljob_processor.go

@@ -143,7 +143,7 @@ func (t *ttlProcessor) work(ctx context.Context) error {
 			return errors.Wrapf(err, "error fetching table relation name for TTL")
 		}
 
-		relationName = tn.FQString()
+		relationName = tn.FQString() + "@" + lexbase.EscapeSQLIdent(primaryIndexDesc.Name)
 		return nil
 	}); err != nil {
 		return err