The most significant changes in this release target reducing the gas consumption
of proof validation and state manipulation.
- Off-chain Window PoSt verification, with dispute mechanism (FIP-0010)
- State size and cache behaviour improvements to HAMT and AMT v3 (FIP-0007)
- Configure optimal branching factor for most HAMTs and AMTs (with state migration)
- Use a Set (nil-value HAMT) rather than Map for pending deal proposals

Other notable changes:
- Replaced miner on-chain seal proof type with Window PoSt proof type
- Market actor accepts deals from miner control addresses
- Remove use of assertions (explicit panic)
- Batch VerifyDealsForActivation
- Scenario testing via agent-based simulation
- Improved migration performance with pre-migration caching and more parallelism