Use buckets for peers.

[kushti]

Currently we're choosing peer to connect at random, which is likely vulnerable to eclipsing. Bitcoin is trying to get connections randomly across IP address space, there were some vulnerabilities found there as well back in 2015: https://www.usenix.org/system/files/conference/usenixsecurity15/sec15-paper-heilman.pdf .

So the goal is about implementing buckets-based strategy with fixes proposed and made in Bitcoin.