fix: allows current sub-agent to finish execution before exiting the loop agent due to a sub-agent's escalation. This commit also disables the summarization for exit_loop tool

[copybara-service]

fix: allows current sub-agent to finish execution before exiting the loop agent due to a sub-agent's escalation. This commit also disables the summarization for exit_loop tool

Fixes #423

Related to #1670

• This avoids the GeneratorExit error thrown, which would crash OTel metric collection and cause Failed to detach context error.
• This also allows all function calls are processed when exit_loop is called together with other tools in the same LLmResponse.

A sample agent for testing:

from google.adk import Agent
from google.adk.agents.loop_agent import LoopAgent
from google.adk.tools.exit_loop_tool import exit_loop

worker_1 = Agent(
    name='worker_1',
    description='Worker 1',
    instruction="""\
Just say job #1 is done.

If job #1 is said to be done. Call exit_loop tool.""",
    tools=[exit_loop],
)

worker_2 = Agent(
    name='worker_2',
    description='Worker 2',
    instruction="""\
Just say job #2 is done.

If job #2 is said to be done. Call exit_loop tool.""",
    tools=[exit_loop],
)

work_agent = LoopAgent(
    name='work_agent',
    description='Do all work.',
    sub_agents=[worker_1, worker_2],
    max_iterations=5,
)

root_agent = Agent(
    model='gemini-2.0-flash',
    name='hello_world_agent',
    description='hello world agent that can roll a  check prime',
    instruction="""Hand off works to sub agents.""",
    sub_agents=[work_agent],
)