List callable models in the OpenAI `model` list shape

Returns every model that can be called right now, chat models first. id is the model call name accepted by every /v1 and /api/v1 operation; owned_by is the model publisher.

Besides the four OpenAI fields, every item carries modality, task and its price in credits (the same object as on /api/v1/models). Chat models (task: chat, the only ones the chat operations accept) also carry context_length, max_output_tokens and supported_parameters. OpenAI SDKs ignore the extra fields. Pass modality=text to list only chat models. Only video models work on POST /v1/videos.