[FEA] .env file loader for native running

[lmeyerov]

Is your feature request related to a problem? Please describe.

When using the experimental native loading support (cd src/python && streamlit ...), the .env is not used. It'd be helpful if it was -- currently a non-obvious workaround like env $(cat .env | xargs) streamlit ... is required .

Describe the solution you'd like

If a .env is locally available, or passed in (ENV_FILE=... streamlit), it should be recognized

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context

The pydantic env package has a convenient abstraction that we use elsewhere for this

[lmeyerov]

cc @DataBoyTX