Feature: subscriber iteration support

[Lancetnik]

We should support alternative way to consume messages instead of decorator callbacks

I think, iteration should be impelemnet something like this

subscriber = broker.subscriber("test")
...
async for msg in subscriber:
    ...

This functional is pretty close to subscriber.get_one() already exists - https://github.com/airtai/faststream/blob/main/faststream/broker/subscriber/proto.py#L90

Also, implementation should be close to this method as well - https://github.com/airtai/faststream/blob/main/faststream/nats/subscriber/usecase.py#L369 , but use native underlying libraries iterations everywhere it is possible

[dearkafka]

I would greatly appreciate if this feature would be realised in future

[Lancetnik]

It will be for sure, but I don't know how soon

[ApostolFet]

I've taken this issue to work