use Python decorator to simplify the registration process

[sonichi]

          This design is great, which can help many applications and agents in multi-agent scenarios.

1. Can we use Python decorator to simplify the registration process? (Not a big issue. Just thinking loud).

class ChildAgent(ResponsiveAgent):
     @register(MathAgent)
     def reponse_for_math_agent(...):
           ...

2. Why use "class_type" as a decision variable. The agent's name can ne another thing to consider (e.g., in the OptiGuide example, where both Writer and Safeguard are ResponsiveAgent).

Originally posted by @BeibinLi in #1165 (comment)