Gossip dynamic local listener ports to peers

[teor2345]

Motivation

Previously, Zebra would either:

• gossip port 0, which is an invalid port for outbound connections, or
• skip gossiping its own dynamically allocated listener port, because the value 0 is invalid.

These changes help test PRs #2273, #2275, and #2276.

API Reference

Binding with a port number of 0 will request that the OS assigns a port to this listener. The port allocated can be queried via the local_addr method.

https://docs.rs/tokio/1.6.1/tokio/net/struct.TcpListener.html#method.bind

Solution

• Configure the address book with the actual listener port, not the configured one
• Improve "no configured peers" warning
• Test that dynamic and fixed ports propagate correctly to the address book

This fix changes the following parts of Zebra's startup order:

• open the listener
  • do the wrong port check
• use its actual address to initialize the TimestampCollector and AddressBook
• (unchanged startup tasks)
• create the listen guard with the previously opened listener
• (more unchanged startup tasks)

Review

@jvff can review this change.

This is a low-priority change, but it's useful for local testing of PRs #2273, #2275, and #2276.

This PR is based on #2276, it should automatically rebase on main once that PR merges.

Reviewer Checklist

• Code implements Specs and Designs
• Tests for Expected Behaviour
• Tests for Errors

[teor2345]

I need to write a unit test that initializes zebra-network, then checks the port in the local listener address.

[teor2345]

There was a mainnet large blocks sync failure, but it might have been due to bad peers?
https://github.com/ZcashFoundation/zebra/pull/2277/checks?check_run_id=2871967768

I restarted all the CI jobs.

[jvff]

Really nice refactor in the peer_set/initialize.rs 🎉

[teor2345]

I need to write a unit test that initializes zebra-network, then checks the port in the local listener address.

Unfortunately I still need to write this test!

But it should be quick.