chore: refactor configs

[mfaizanse]

Description

Changes proposed in this pull request:

• Remove support for .env.test file.

Related issue(s)

• Improve Secret Management and Test Configuration Handling #343

[github-actions]

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• If any changes are made to how to run the unit tests, make sure to update the steps for unit-tests in the create-release.yml workflow as well.

Note(s) for PR Reviewer(s):

• Make sure that the integration and evaluation tests are working as expected.

[muralov]

nitpick: you can use lru_cache if you want to avoid global variable. You can search other places of companion that is used.

@lru_cache(maxsize=1)
def init_proxy_client() -> BaseProxyClient:
    """Initialize the proxy client for the GenAI Hub only once."""
    return get_proxy_client("gen-ai-hub")

[muralov]

just a comment, you don't have to do it now.

We need to share the model logic from a shared package. There is an issue already we'll do it later.