[RND-176] Allow comet_llm in Python Panels

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This PR allows comet_llm.API() to get config settings from streamlit environment.

Requires: https://github.com/comet-ml/comet-python-client/pull/2407

How to test?

1. Put the following in a file named page_test.py ("page_" is required).
2. Run with streamlit run page_test.py

import streamlit as st
import os
if "comet_config_override" not in st.session_state:
    st.session_state["comet_config_override"] = {}
key = os.path.basename(__file__)
config = {
    "comet.url_override": 'https://www.comet.com/clientlib',
    "comet.api_key": 'YOUR-API-KEY',
    "comet.workspace": 'YOUR-WORKSPACE',
    "comet.project_name": 'YOUR-PROJECT',
    "COMET_EXPERIMENT_KEYS": ["YOUR-EXPERIMENT-KEY"],
    "COMET_PANEL_OPTIONS": {},
}
st.session_state["comet_config_override"][key] = config
# User code:
from comet_llm import API
import streamlit as st

api = API()

st.write(api)

If it doesn't work, you'll get an API key error. Otherwise, it will display the methods of api.

See also tests in comet_ml: https://github.com/comet-ml/comet-python-client/blob/master/comet-client-lib/tests/unit/test_streamlit.py

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I'm going to rewrite this so as not to expose streamlit stuff in comet_llm. I'll make a function to get the class over in comet_ml.

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Ready for review.

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This now works with changes in comet_ml.