Observability for streaming models

[cmasantos]

Hi, I've notice that "normal" chat model produce a set of gen_ai* metrics. But I've been unable to use them with streaming models. Also when we use a combination of Mutiny StreamingResponseHandler I'm almost sure that it can't be done.

My question is, how can I add metrics to a streaming model even if need to instantiate them? I've found the MetricsChatModelListener class but I can't find a way to put it together with the streaming model interface.

[geoand]

Good idea to bring it up!

I opened #1081