* (feature)(cloud) Use dynamic allocator instead of static buffer pool for better elasticity. (#28983)
* [fix](outfile) Fix unable to export empty data (#30703)
Issue Number: close#30600
Fix unable to export empty data to hdfs / S3, this behavior is inconsistent with version 1.2.7,
version 1.2.7 can export empty data to hdfs/ S3, and there will be exported files on S3/HDFS.
* [fix](file-writer) avoid empty file for segment writer (#31169)
---------
Co-authored-by: AlexYue <yj976240184@gmail.com>
Co-authored-by: zxealous <zhouchangyue@baidu.com>
If the original data is：
```sql
+-----------------------------------------------------+
| s_info |
+-----------------------------------------------------+
| {"s_id": 2, "s_name": "nereids", "s_address": "20"} |
| {"s_id": 1, "s_name": "doris", "s_address": "18"} |
+-----------------------------------------------------+
```
In the original logic, the struct type data exported to a csv file format did not contain column names,like
```
{2, "nereids", "20"}
{1, "doris", "18"}
```
This pr do not need to be merged into branch-2.0
This pr makes three changes to the display of complex types：
1. NULL value in complex types refers to being displayed as `null`, not `NULL`
2. struct type is displayed as "column_name": column_value
3. Time types such as `datetime` and `date`, are displayed with double quotes in complex types. like
`{1, "2023-10-26 12:12:12"}`
This pr also do a code refactor:
1. nesting_level is set to a member variable of the `DataTypeSerDe`, rather than a parameter in methods.
What's more, this pr fix a bug that fileSize is not correct, introduced by this pr: #25854
