feat: implement FRC-0089 EC finality calculator

[hanabi1224]

Overview

Implement the EC (Expected Consensus) finality calculator as specified in FRC-0089.

Background

FRC-0089 proposes a dynamic finality calculator for Filecoin that considers observed chain history to attain finality guarantees more efficiently than the current static 900-epoch threshold. The calculator can achieve a 2^{-30} error probability in approximately 30 epochs (~15 minutes), a ~30x improvement over the current approach.

References

• FRC-0089 spec: https://github.com/filecoin-project/FIPs/blob/master/FRCs/frc-0089.md
• Reference implementation: https://github.com/consensus-shipyard/ec-finality-calculator

Related

• Raised during review of chore(deps): bump go deps #6757