ref: Remove lifetime annotations from ArroyoConsumer

[lynnagara]

This is an attempt to simplify the ArroyoConsumer lifetimes by
changing the LocalConsumer to have ownership of the LocalBroker.

Since this consumer/broker only used in place of the KafkaConsumer
for testing, I think this change is fairly harmless as it's not
required for the broker to live outside the consumer.

[fpacifici]

We would have a problem if the consumer owns the broker: you cannot share a broker between a producer and a consumer if you are testing that scenario.
I would not drop that scenario.

[lynnagara]

@fpacifici But there is no such producer in this library. Just a produce method on the broker. It seems you are implying some pretty big changes to how this works currently - that there is going to be a local producer who gets a reference to a broker.

[fpacifici]

https://github.com/getsentry/arroyo/blob/main/arroyo/backends/local/backend.py#L356

We have the local producer in Arroyo. Originally I did not port it just because I did not have time but that was the intention. Any reason for not doing it in the rust version ?