[Persistence] State Hash Computation Implementation

[Olshansk]

Objective

Compute a hash in order to take a snapshot of the V1 state via a single hash.

Origin Document

See the entire conversation around the state hash in https://github.com/pokt-network/pocket-network-protocol/tree/main/persistence.

Goals / Deliverables

• Determine if we should use a Merkle Tree or Vector Committments
• Pick a library for the merkle Tree or commitments
• Compute and expose the state hash after every block commit
• Incorporate the schemas (i.e. protobuf message definitions) in the state hash
• Create a foundation to enable fast sync and slow sync by synching the different state trees
• Do not limit the trees to only be keyed by addresses

General issue checklist

• Update the appropriate CHANGELOG
• Update the README
• If applicable, update the source code tree explanation
• If applicable, add or update a state, sequence or flowchart diagram using mermaid
• Update any relevant global documentation & references
• Document small issues / TODOs along the way

Non-goals

• TODO

Testing Methodology

• Develop an appropriate test suite
• All tests: make test_all
• LocalNet: verify a LocalNet is still functioning correctly by following the instructions at docs/development/README.md
  Remove

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Creator: @Olshansk
Co-Owners: @andrewnguyen22

[Olshansk]

The team's internal research is being aggregated here and will be shared publically once complete. If you would like access aprior, please reach out to the team and we'd be happy to share.

We are currently planning to use [https://github.com/celestiaorg/smt] originally implemented by @musalbas because:

• It is a simple implementation of Libra's Jellyfish Merkle Tree
• Takes advantage of the two major Sparse Merkle Tree optimizations: empty subtrees and single-node subtrees
• Fully implemented in Go
• Much simpler than Ethereum's modified Merkle Patricia Trie in both implementation and logic complexity

The work is currently ongoing in this branch: https://github.com/pokt-network/pocket/pull/new/issues/147/statehash