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
`ExternalFileTableValuedFunction` now has 3 derived classes:
- LocalTableValuedFunction
- HdfsTableValuedFunction
- S3TableValuedFunction
All these tvfs are for reading data from file. The difference is where to read the file, eg, from HDFS or from local filesystem.
So I refine the fields and methods of these classes.
Now there 3 kinds of properties of these tvfs:
1. File format properties
File format properties, such as `format`, `column_separator`. For all these tvfs, they are common properties.
So these properties should be analyzed in parenet class `ExternalFileTableValuedFunction`.
2. URI or file path
The URI or file path property indicate the file location. For different storage, the format of the uri are not same.
So they should be analyzed in each derived classes.
3. Other properties
All other properties which are special for certain tvf.
So they should be analyzed in each derived classes.
There are 2 new classes:
- `FileFormatConstants`: Define some common property names or variables related to file format.
- `FileFormatUtils`: Define some util methods related to file format.
After this PR, if we want to add some common properties for all these tvfs, only need to handled it in
`ExternalFileTableValuedFunction`, to avoid missing handle it in any one of them.
### Behavior change
1. Remove `fs.defaultFS` property in `hdfs()`, it can be got from `uri`
2. Use `\t` as the default column separator of csv format, same as stream load
