Design Epoch Mechanism

[bfish713]

Epochs are the time periods where the stake table should be fixed and any changes to the table will be applied at the end of an epoch and be valid for the duration of the epoch.

Some things we need to address:

• How will epoch transitions mesh with view sync, especially considering when views near epoch boundaries timeout or when view sync syncs on a epoch boundary
• Which block/leaf will we use for the stake table of the new epoch? Most recent decided state?
• How will catchup know get the epoch we are in
• For epoch transitions what logic will we have to change. Specifically what places do we currently check for leaders of future views (e.g sending a DA proposal 3 views before we are leader)