[refactor] Rename operators and revise op structure at 2025-08-21

[SunnyHaze]

What's changed

The file structure of dataflow/operators has been remanaged to this schema for clarity and user friendly:

|-- __init__.py
|-- agentic_rag
|   |-- __init__.py
|   |-- eval
|   |-- filter
|   `-- generate
|-- chemistry
|   |-- __init__.py
|   |-- eval
|   `-- generate
|-- conversations
|   |-- __init__.py
|   |-- consistent_chat.py
|   `-- func_call_operators.py
|-- core_speech
|   |-- __init__.py
|   `-- generate
|-- core_text
|   |-- __init__.py
|   |-- eval
|   |-- filter
|   |-- generate
|   `-- refine
|-- core_vision
|   |-- __init__.py
|   `-- generate
|-- db
|   |-- __init__.py
|   `-- db_operator.py
|-- general_text
|   |-- __init__.py
|   |-- eval
|   |-- filter
|   |-- generate
|   `-- refine
|-- knowledge_cleaning
|   |-- __init__.py
|   `-- generate
|-- pandas_operator.py
|-- rare
|   |-- __init__.py
|   `-- generate
|-- reasoning
|   |-- __init__.py
|   |-- eval
|   |-- filter
|   `-- generate
`-- text2sql
    |-- __init__.py
    |-- eval
    |-- filter
    `-- generate