Support custom openai base url in config_list_openai_aoai

[thinkall]

Add support to custom openai base url

[sonichi]

Why do we need this?

[thinkall]

Why do we need this?

To support local models. Currently, if a local model is defined with environment variables, it won't work.

[sonichi]

Why is that? Does openai's Client ignore the base_url?

[thinkall]

Why is that? Does openai's Client ignore the base_url?

If the config is loaded by config_list_openai_aoai, then no base_url will be set. Currently, config_list_from_models will trigger the bug.