feat: integrated name service contract

[Alejandro-Morales]

Integrated name service contract to uAgents.
New almanac contract with name service integration: "fetch1h5rhtj5m6dqjmufj5m3t4mq6l7cnd8dvaxclwmrk6tfdm0gy3lmszksf0s"

Name service contract:
"fetch1yrf4xpglq02fzj50m9wn44qdq89a5vr0ufa42qa506uhwal4n79s99sp87"

When an agent is running, it will register in alamanac contract

To register on name service contract, you need to use the helper function agent.register_name() it will then register the agents name under the agent domain.

Agents can now query the name service contract by providing the agent name, the following will return the agent address:
get_agent_address("agent_name_to_query")

Also you can now communicate with other agents using their registered name:

ctx.send("bob", Message(message="Hello there bob."))

[MissingNO57]

LGTM

[jrriehl]

Looks good, I'm just thinking in the interests of keeping the agent class as uncluttered as possible, it might be better to move all the contract stuff to network.py.