Changes to GET /v1/models

the response property data/items/context_length became nullable for the status 200

added the new optional query request parameter output_modalities

added the optional property data/items/capabilities to the response with the 200 status

added the optional property data/items/max_output_tokens to the response with the 200 status

added the optional property data/items/supported_service_tiers to the response with the 200 status