importccl: fix bug when mixing old and new tables during import

There was an indexing bug which would have been triggered if the
resolution of new and old table descriptors was ever mixed within the
same import. This situation has not hit any users because an IMPORT only
allows writing to new tables, while an IMPORT INTO only allows writing
to existing (old) tables, thereby never mixing the two.

This change fixes that bug.

Closes cockroachdb#50733

Release note: None

pkg/ccl/importccl/import_stmt.go

@@ -1014,7 +1014,8 @@ func (r *importResumer) prepareTableDescsForIngestion(
 			if err != nil {
 				return err
 			}
-			for i, table := range res {
+			for _, table := range res {
+				i := newTableDescToIdx[table]
 				importDetails.Tables[i] = jobspb.ImportDetails_Table{Desc: table,
 					Name:       details.Tables[i].Name,
 					SeqVal:     details.Tables[i].SeqVal,