A long running public testnet

# Background

Once mainnet comes around, there will be no testnet with low stakes and easy access.

# Proposal

We launch a long running public testnet, which has `sudo` perpetually, which aims to be the primary playground where developers, infrastructure providers, testers and workers can practice and learn, and also the final testing group for new runtime upgrades. Genesis block can be super centralized, as it will not be a value bearing network, which the perpetual `sudo` pallet should ensure as well. **There is an open problem about what to do about governance and roles on such a network, not sure about that.**