* Allow to have more than min_peers/2 outbound peers
Default value is 8, so we allow only 4 outbound peers, unfortunately if a node is behind NAT it can't get inbound peers and it stucks with 4 peers as maximum.
This PR allows a number of outbound peers to be between min_peers and max_peers/2. Node behind NAT will eventually have just min_peers number of peers.
* Extract into healthy_peers_mix function
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