[fix](prepare) fix datetimev2 return err when binary_row_format (#34662)

fix datetimev2 return err when binary_row_format. before pr, Backend return datetimev2 alwary by to_string.
fix datatimev2 return metadata loss scale.

fe/fe-core/src/main/java/org/apache/doris/mysql/MysqlSerializer.java

@@ -298,6 +298,8 @@ public class MysqlSerializer {
             case DECIMAL64:
             case DECIMAL128:
             case DECIMAL256:
+            case TIMEV2:
+            case DATETIMEV2:
                 return ((ScalarType) type).decimalScale();
             case FLOAT:
             case DOUBLE: