On-chain validator identification

# Background

Right now there is no identifying information for Joystream validators on-chain:


Contrast this with validator information present on a chain like Polkadot:


So far as I understand, this information comes from the registrars in the `pallet_identity`, which is part of the Polkadot runtime.

The lack of accurate information about the identity of different validators will substantially increase the cost for nominators to distinguish validators in terms of quality, meaning that there will be less stake deployed, and more of that stake will be deployed inefficiently, i.e. with wasteful tradeoffs between quality and commission rates. That may ultimately go as far as impacting the quality of the overall validator set of the chain, in terms of security, uptime, etc.

# Proposal

This information has to be accountable to the governance of the chain in some way, otherwise, it is unlikely to work well. There are two approaches it seems, try to enhance Pioneer to show some sort of validator screen where some sort of verification information is shown, or to use the same system as the rest of the Dotsama ecosystem. The benefit of using this approach is that its already going to work well with lots of other tools, such as dashboards, staking service providers, and wallets. The con is that we have to introduce a new pallet, `pallet_identity`, and probably a new proposal that allows the council to add registrars (`add_registrar`).

Before this is done both the new pallet and Polkadot.js should be reviewed to make sure what is described here is correct.