[Bug]: The to_dict() method in the schema does not completely convert an object to a json dict, datatype and function type are still an IntEnum class

[zhuwenxing]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

The to_dict() method in the schema does not completely convert an object to a json dict, datatype and function type are still an IntEnum class

Expected Behavior

DataType/FunctionType object can be represented as a dictionary

    def to_dict(self) -> dict:
        """Convert DataType to a plain dictionary.
        
        Returns:
            dict: A dictionary containing the name and value of the DataType.
        """
        return {
            "name": self.name,
            "value": self.value
        }
    
    @classmethod
    def from_dict(cls, d: dict) -> "DataType":
        """Create DataType from a dictionary.
        
        Args:
            d (dict): Dictionary containing DataType information.
                     Must have either 'value' or 'name' key.
        
        Returns:
            DataType: The corresponding DataType enum value.
        """
        if "value" in d:
            return cls(d["value"])
        return cls[d["name"].upper()]

Steps/Code To Reproduce behavior

No response

Environment details

- Hardware/Softward conditions (OS, CPU, GPU, Memory):
- Method of installation (Docker, or from source):
- Milvus version (v0.3.1, or v0.4.0):
- Milvus configuration (Settings you made in `server_config.yaml`):

Anything else?

No response