Support execution for simple agents

[rickycambrian]

I'm finding the library to work fantastic, but got to the point where I also wanted to call on agents, so I made some changes to support calling on agents. This is confirmed to work on my agent using GET and params passed in the url. I think some further adjustments will be needed to make sure different types of agents and edge cases are well supported, but I thought I would share what is working well from my end within the context I am working in.

Here is an example of how a paid request is made:

from agent0_sdk.core.x402_client import X402Client
from agent0_sdk.core.agent_client import AgentClient

x402 = X402Client(
    rpc_url=os.getenv("RPC_URL"),
    private_key=os.getenv("PRIVATE_KEY"),
    chain_id=11155111
)

agent = AgentClient(
    agent_card_url="https://agent.example.com/.well-known/ai-plugin.json",
    x402_client=x402
)

result = agent.call("What is Ethereum?")

[rickycambrian]

This one should have been a draft for continued development, sorry about that. This PR on the typescript library side seems promising: agent0lab/agent0-ts#13 once this or similar PR is merged elsewhere, I will adapt the python side accordingly if we don't get a similar PR for parity on the python side