[fix](function) fix Substring/SubReplace error result with input utf8… (#40954)
… string (#40929)
https://github.com/apache/doris/pull/40929
```
mysql [(none)]>select sub_replace("你好世界","a",1);
+-------------------------------------+
| sub_replace('你好世界', 'a', 1) |
+-------------------------------------+
| �a�好世界 |
+-------------------------------------+
mysql [(none)]>select SUBSTRING('中文测试',5);
+------------------------------------------+
| substring('中文测试', 5, 2147483647) |
+------------------------------------------+
| 中文测试 |
+------------------------------------------+
1 row in set (0.04 sec)
now
mysql [(none)]>select sub_replace("你好世界","a",1);
+-------------------------------------+
| sub_replace('你好世界', 'a', 1) |
+-------------------------------------+
| 你a世界 |
+-------------------------------------+
1 row in set (0.05 sec)
mysql [(none)]>select SUBSTRING('中文测试',5);
+------------------------------------------+
| substring('中文测试', 5, 2147483647) |
+------------------------------------------+
| |
+------------------------------------------+
1 row in set (0.13 sec)
```
## Proposed changes
Issue Number: close #xxx
<!--Describe your changes.-->