Define voting HIR format

[zeegomo]

Define High Level Intermediate Representation (HIR) for voting entities in the Catalyst ecosystem.
This is intended as a high level description of the setup, which is not enough on its own to spin a blockchain, but it's slimmer, easier to understand and free from implementation constraints.
You can roughly read this as "voting_key will participate in this voting round with role voting_group and will have voting_power influence"

This builds on the concept of voting groups as described in input-output-hk/vit-servicing-station#198

This is an intermediate step in the proposed process of spinning up a blockchain from the raw mainnet snapshot.

Such process is planned to look as follow:

• collect valid catalyst registrations (db-sync + Adrestia's voting tools)
• collect valid representative registrations (TBD)
• aggregate all registrations and produce a single set of participants in the voting event ( snapshot tool in this repo)
• setup blockchain parameters (block0, ...) and spin up nodes (vitup)

Not sure if catalyst toolbox is actually the correct place to host this.