repair: Add repair_row_on_wire_with_cmd

It is used to contain both a repair cmd and repair_row_on_wire object.

repair/repair.hh

@@ -320,6 +320,12 @@ struct repair_hash_with_cmd {
     repair_stream_cmd cmd;
     repair_hash hash;
 };
+
+struct repair_row_on_wire_with_cmd {
+    repair_stream_cmd cmd;
+    repair_row_on_wire row;
+};
+
 enum class row_level_diff_detect_algorithm : uint8_t {
     send_full_set,
 };