[FEATURE] Support non-stream in OpenAIModel

[howardzhou]

Problem Statement

Currently OpenAIModel only supports stream=True
Some model does not support that.
So I'd like to have an option with stream=False in OpenAIModel.

Proposed Solution

Similar implementation for Bedrock API with stream=False
3100ea0

Use Case

model = OpenAIModel(
    # can also pass dict as first argument
    client_args={"api_key": "abc123", "base_url": "http://localhost:8009/v1"},
    stream=False,
    # everything from this point is a kwarg though
    model_id="xxx",
)

agent = Agent(model=model, tools=[calculator])
agent("What is 2+2?")

Alternatives Solutions

No response

Additional Context

No response