[Consensus] Formalize Attacks

[sternhenri]

• This epic will hopefully help resolve a lot of the underlying GH issues related to specific attacks
• Through this epic, we work through a more formal model for understanding EC, which will be usable elsewhere

Short Term

• Pin down dependencies section setting up attack work (ie write down agreed upon EC construction to evaluate)
• Do initial analysis of each attack:
  • Challenge Grinding or multi-chain forking
  • Nothing at Stake
  • Selfish Mining
  • Posterior Corruption

Medium Term

• Present the above for FIL research week to iterate in person
• Select and bring in relevant outside researchers to critique/pursue work