Parallel State Root Calculation

Labels: reth, execution, scalability

Summary:
Stabilize and optimize the Reth Parallel State Root feature in Metis SDK. Allow concurrent processing of Merkle tree updates across account trie branches and accelerate final state commitment.

Subtasks:

• Merge stable Reth upstream implementation.
• Optimize intra-tree concurrency model.
• Provide benchmarking tools for state root throughput.

Rationale:
State root calculation is a critical bottleneck in block finalization. Parallelization reduces bottlenecks in block production and ensures faster transitions between blocks.