GoogleGenerativeAI streaming

[gomander]

The @google/generative-ai package exposes a somewhat different API than the openai and @anthropic-ai/sdk packages do. This is clearest in the implementation of streaming responses.
The others expose a .toReadableStream() method on the return value of their streaming methods. Google does not do this, instead returning an AsyncGenerator.
I've tried to find a way to convert the output into a ReadableStream, but nothing I've tried has worked. I suspect that there is a fairly simple solution, I just don't have the experience with streams required to find it.

For now, using the GoogleAI API will just force streaming to be disabled.