EPIC: Ethereum Addressing

[Stebalien]

• [x] Implement f4 address support
  • PR: https://github.com/filecoin-project/ref-fvm/pull/860
  • [ ] Add a checksum? Still TBD.
• [x] Implement an embryo actor
  • PR: https://github.com/filecoin-project/builtin-actors/pull/667
  • [x] And a bug fix https://github.com/filecoin-project/builtin-actors/pull/694
• [ ] Integrate the embryo actor into the ref-fvm
  • PR: https://github.com/filecoin-project/ref-fvm/pull/897
• [ ] Store the "predictable" address (f1/f3/f4) in the root "actor object" (pending https://github.com/filecoin-project/FIPs/discussions/459#discussioncomment-3666005).
  • PR: TODO
• [ ] Implement EAM actor.
  • PR: https://github.com/filecoin-project/builtin-actors/pull/695