Make `interrupted` an agent state and make it not final. As a result, a
`wait` won't return on an interrupted agent and no notification will be
send to the parent agent.
The rationals are:
* If a user interrupt a sub-agent for any reason, you don't want the
parent agent to instantaneously ask the sub-agent to restart
* If a parent agent interrupt a sub-agent, no need to add a noisy
notification in the parent agen
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