refactors to abolish the lotus <> test-vectors circular dependency

[raulk]

• Simplify the schema to not use Filecoin-specific types (thus removing dependencies on go-state-types). Refactor where necessary.
• Turn the schema into a standalone go module, adding a local replace directive here to streamline development.
• Migrate the chaos actor to the Lotus repo.

---

Part of filecoin-project/lotus#3666.

[raulk]

Had to update these vectors because the schema changed slightly, and the previous vectors became unparseable.

[alanshaw]

LGTM