Check that the authority-discovery module discovers all (or almost all) validators

[tomaka]

#6614 adds a new metric that reports the number of validators known to the authority-discovery module.

This issue is a reminder that, after this PR has been merged and deployed on our nodes, we should check if it reports a correct value.

[tomaka]

The metric is now on 8 nodes, and they seem to be somewhere between 14 and 16 known validators.

[mxinden]

As of today the authority-discovery module is still disabled by default on Polkadot: https://github.com/paritytech/polkadot/blob/master/cli/src/cli.rs#L62-L72. I would still expect a node to find more validators as at least Parity and web3 are enabling this feature.

[tomaka]

Everything seems to work fine on Kusama!

The number is now almost at 200, and nothing significant has happened.

Polkadot validators are still in the process of upgrading, but everything seems to work well too.

[tomaka]

Closing this as done 🎉