[Feature Request] Expose `strict_json_schema` argument in `activity(nexus)_as_tool` in OpenAI SDK integration


Currently, the OpenAI SDK integration hardwires `strict_json_schema=True` in https://github.com/temporalio/sdk-python/blob/main/temporalio/contrib/openai_agents/workflow.py#L152 and L238 . 

The current workaround is to use `dataclasses.replace` on the result, but it could be cleaner to pass it as an argument to `activity_as_tool`, as suggested by a Temporal customer... 
