Consider removing AgentAction class

[evangriffiths]

This is a class for making Functions/tools that the microchain agent uses to get/change properties about itself. The class has an Agent property, which seems like the wrong way round (i.e. an agent should have a tool).

See thread here #222 (comment)

[coderabbitai]

Ah I guess this is necessary only because of agent's functions?

functions.extend([f(agent=agent) for f in AGENT_FUNCTIONS])

So if #253 is resolved, this dummy build_agent could be replaced with build_agent_functions.