Optimize farm and cache identification

[nazar-pc]

Currently farming cluster operates on farms and caches without any knowledge of "farmer".

This works and is flexible, but results in a bit too many notifications from identification messages, which #2899 improve a little bit.

It might be beneficial to also associate farms with farmers (and similarly for caches), just some ephemeral identifier, such that we can reduce identification broadcast from one per farm to one per farmer most of the time.

Farm identification as such should likely be replaced with a stream request such that farmer can send a stream of responses back to controller at a sustainable rate rather than bursting potentially thousands of messages all at once that might be dropped by NATS server due to buffer limits.

[tediou5]

let me work on this. Its looks easy