Add support for translation endpoint

[stuartleeks]

See https://learn.microsoft.com/en-us/azure/ai-services/openai/reference#translations

• add generator for translations and include in default generators
• validate translation endpoint with record/replay
• determine how rate-limiting is applied and add to the simulator rate-limiting
• add tests
• add load test

(from stuartleeks/aoai-simulated-api#47)

[wtulloch]

@stuartleeks I will try this one