Hard Forks and Optimistic Conf

[aeyakovenko]

Problem

Hard Forks are going to be hard.

1. Abandonded blocks after the hardfork may have votes

Proposed Solution

1. Votes after the optimistic block need to be ignored for optimistic configuration after restart.
2. after snapshot is enabled, we should set a --min-optimistic-slot=X, where X is the root slot where the clients should start accepting new optimistic blocks. Until that point full finality needs to be reached. Maybe it's easier to do it in the next epoch

tag: @carllin