Finality Certificate Exchange Protocol

Goal: Given a granite root, a client can discover, fetch and verify finality certificates.

Requirements:

• Network isolation (multiple instances of granite can exist in libp2p net), granite networks will have their names.
• Hello protocol for bootstrap (what is the latest cert your know of)
• Fetching range of finality certificates (we can use heights/epochs as granite things are final)
• Verification of these certificates (it is sequential)
• After verification and sync, store the result in Certificate Store.