feat: peer selection for protocols

[weboko]

This is a feature request

Problem

Currently we select peers for use by protocol as it is - just by fetching them from peer store.

It is not a problem by itself but it impacts some features we want to implement such as:

• LightPush message verification via Filter;
• LightPush message verification Store;

It also theoretically increases footprint of a light node in the network and thus making it more stable.

Proposed Solutions

Peer selection mechanism based on priorities:

• when peer pool is getting filled - select those that are not used by other protocols;
• if no peers available use any available;

This also should be a part of renewal mechanism.