feat: Add parallel state root computation support for Bonsai trie

[matkt]

PR description

Description

This PR introduces parallel processing capabilities for Merkle Patricia Trie operations during state root computation in Bonsai storage format, significantly improving block validation performance.

Changes

Core Implementation

• ParallelStoredMerklePatriciaTrie: New parallel implementation of StoredMerklePatriciaTrie
  • Batches pending updates (puts/removes) before processing
  • Recursively processes branch children in parallel using ForkJoinPool
  • Handles branch, extension, leaf, and null node scenarios

Configuration

• WorldStateConfig: Added isParallelStateRootComputationEnabled flag (default: true)
• PathBasedExtraStorageConfiguration: Added parallel state root computation configuration
• CLI Option: --bonsai-parallel-state-root-computation-enabled to enable/disable feature

Key Features

1. Parallel Branch Processing: When a branch node has multiple children with updates, they are processed concurrently
2. Extension Node Expansion: Extensions are temporarily expanded into branches when beneficial for parallel processing
3. Leaf/Null Node Handling: Intelligent expansion into branch structures when multiple diverging updates exist
4. Smart Partitioning: Updates are grouped by size - large groups processed in parallel, small groups sequentially
5. Commit Cache: Thread-safe caching of node updates during parallel processing

Backward Compatibility

• Feature is opt-in via configuration flag (though enabled by default)
• Falls back to sequential StoredMerklePatriciaTrie when disabled
• No breaking changes to existing APIs
• Fully compatible with existing Bonsai storage format

Configuration Examples

# Enable (default)
besu --data-storage-format=BONSAI --bonsai-parallel-state-root-computation-enabled=true

# Disable for comparison/debugging
besu --data-storage-format=BONSAI --bonsai-parallel-state-root-computation-enabled=false