[OPIK-1812] Implement a function for recursive callback passing in adk

[alexkuzmik]

Details

Implemented a new experimental feature - track_adk_agent_recursive function. It allows to not pass the callback function to every agent component manually. Instead it iterates over subagents and tools, searches for BaseAgent or AgentTool instances and recursively propagates opik callbacks to them.

    opik_tracer = OpikTracer()

    translator_to_english = adk_agents.Agent(
        name="Translator",
        model=MODEL_NAME,
        description="Translates text to English.",
    )
    summarizer = adk_agents.Agent(
        name="Summarizer",
        model=MODEL_NAME,
        description="Summarizes text to 1 sentence.",
    )
    root_agent = adk_agents.SequentialAgent(
        name="TextProcessingAssistant",
        sub_agents=[translator_to_english, summarizer],
        description="Runs translator to english then summarizer, in order.",
    )

    track_adk_agent_recursive(root_agent, opik_tracer)

The calls of track_adk_agent_recursive are idempotent so it should be safe to call it multiple times or to call it for the agent which already contains OpikTracer callbacks (or which has subagents/agent tools already containing OpikTracer callbacks)

Testing

Added integration tests.

Documentation

Added docstrings.