design: minimal delegation

[just-mitch]

We need a design for a minimal delegation mechanism for the first permissionless testnet.

The key requirements are demonstrated in the following flow:
Suppose Alice holds some hypothetical asset that allows her to run a validator on Aztec, but she would rather delegate to a professional node operator, Bob.

Alice should be able to do that, with the additional guarantees:

• Any hypothetical rewards that Bob would receive could be shared with her
• Alice can vote on governance proposals with her delegated stake
• Alice can withdraw her delegation without Bob's consent/action