Bootstrap Certificate Chain w/ Genesis Certificate

[jpraynaud]

Issue

Create a genesis command of the Aggregator (manual operation):

• (Re)Use a private key (Cardano keys) for testing purpose
• (Re)Use a public key stored on a public location (Github)
• Create and store a Genesis Certificate that embeds the AVK of the Stake Distribution and its Genesis Signature in the Aggregator
• Verify the Genesis Certificate in the Client
• Implement this feature in the End to End Tests

Tasks

• Add a Genesis Signer that signs a message with a Genesis Secret Key (only for test purpose)
• Add a Genesis Verifier that verifies a Genesis Signature against a Genesis Verification Key
• Implement the verify_genesis_certificate of the Certificate Verifier
• Make Client load/use the Genesis Verification Key
• Make Aggregator load/use the Genesis Verification Key
• Make Aggregator verify that the Certificate Chain is valid before trying to produce new Mithril Certificates
• Add a sub command to the Aggregator CLI to generate test only Genesis Keys, and boostrap a test only Genesis Certificate
• Add a sub command to the Aggregator CLI to export the message that must be signed with Genesis Secret Key into a Genesis Signature
• Add a sub command to the Aggregator CLI to import the Genesis Signature and create a Genesis Certificate
• Update test lab to bootstrap a Genesis Certificate
• Update devnet standalone to bootstrap a Genesis Certificate
• Update GCP Aggregator to use the test Genesis Keys
• Update documentations
• Deploy to GCP Aggregator (and bootstrap Genesis Certificate)

Depends on #316

[jpraynaud]

The Mithril Aggregator hosted on GCP now runs with a Genesis Certificate that guarantees authenticity of the Stake Distribution used to sign 👍

To make a Mithril Signer work on this network, here is a list of tasks to complete:

1. Recompile the Mithril Signer node as explained in this guide
2. Wait until epoch 30 of the preview network before the Mithril Signer node starts producing Individual Signatures