feat(tools): request answer tool factory

[Lin-Nikaido]

Add request_answer_factory as util tool.
This provides a comprehensive handler for tools that require user approvalor interaction.

Example

from google.adk.utils.request_answer_factory import request_answer_factory
requesting_tool, before_agent_callback, after_agent_callback = request_answer_factory("approve", your_tool)

Agent(
    model="your/model-name",
    before_agent_callback=[before_agent_callback]
    after_agent_callback=[after_agent_callback]
    tools=[requesting_tool]
)