feat: change the Artifact to be folder-based

[yzld2002]

Currently we implement the Artifact based on the pickle.
This requires to load / save the files.

This PR changes the Artifact to be folder-based.
There is no need to load / save any more.
All the files under the cwd (current working directory) will be treated as the files inside the Artifact.

Also we want to keep the chat_with_artifacts running in the same environment with the code_interpreter. So we don't have to maintain "local" and "remote".

---

Local test

Code:

from vision_agent.agent import VisionAgent
from vision_agent.tools.meta_tools import Artifacts


artifacts = Artifacts("/Users/zhichao/Projects/vision-agent-chat/va-local-test")

agent = VisionAgent(verbosity=1)
resp, artifacts = agent.chat_with_artifacts(
    [
        {
            "role": "user",
            "content": "Can you write code to detect the car and visualize the detection?",
        }
    ],
    artifacts=artifacts,
    test_multi_plan=False,
)
resp.append({"role": "user", "content": "Can you describe the output image?"})
resp, artifacts = agent.chat_with_artifacts(resp, artifacts, test_multi_plan=False)

Result:

---

Also tested the view_media_artifact action, the result looks good now.

[dillonalaird]

Thanks for doing this! I think it mostly looks good, just one comment right now

[dillonalaird]

one more comment

[dillonalaird]

Looks good! One minor comment