Disconnect from punished validators on disputes

[eskimor]

In case of a finished dispute, we no longer want to communicate with validators which have been slashed significantly. We should make sure to remove those validators from the reserved set and also ban any connection attempts via free incoming slots.

For request/response we should probably stop using IfDisconnected::TryConnect, so disconnecting validators from peersets is enough to stop any communication with them.

[rphmeier]

cc @andresilva

There is a notion of 'disabled' validators in the FRAME staking / session pallets. We should extend the implmentation to cover the remainder of the current era and communicate 'disabled' validators to the network bridge or other networking subsystems so they can ignore messages.

Ideally, there'd be a round-robin mechanism so if more than f validators are disabled that we start allowing communication from the remaining 2f+e which is necessary to maintain consensus. Otherwise, we risk a liveness error.

[rphmeier]

We should also ignore backing statements from disabled validators on-chain.

[rphmeier]

And potentially also ignore dispute votes of unconfirmed (<1/3 participation) disputes by disabled validators

[eskimor]

Superseded by paritytech/polkadot-sdk#784.