Add third-party agent support to workflows

[psschwei]

As a user, I want to be able to run a non-bee agent using the bee-hive.
We can pick one third-party agent (crewai, langchain, autogen, etc.) and run it as part of #117
To do this, we'll need a way to represent this third party agent via the Agent class

cc @maximilien who seems to inherit most of our inheritance issues 😄

[planetf1]

Update: The two PRs above implement some sample agents, and a workflow change to allow them to be executed. Neither area is complete, and are dependent on other changes (like variable passing). See PRs for more detail