Avoid redundant account multiproofs when dispatching storage-only proofs

[yongkangc]

Summary

dispatch_storage_proof is effectively unused for state-root multiproof work in the execution tree. Every call path funnels through dispatch_multiproof and creates PendingMultiproofTask::Regular, even for storage-only proof requests. This causes redundant account multiproofs when the account proof is already available.

Solution: We should be able to utilize storage-only proofs to not do redundant account multiproofs, when we already had the account proof fetched before.

Currently, dispatch_storage_proof is only used in crates/trie/parallel/src/proof.rs and provides no benefit for the state-root computation path in the engine tree.

In the engine tree's multiproof processor, we always invoke:

• MultiproofInput { ... }.into() during prefetch
• MultiproofInput { ... }.into() during state updates

Both convert directly into PendingMultiproofTask::Regular.

StorageMultiproofInput and PendingMultiproofTask::Storage are never constructed in the execution flow.

References

• Main file: crates/engine/tree/src/tree/payload_processor/multiproof.rs
• Storage proof worker: crates/trie/parallel/src/proof.rs
• Related PRs: perf(tree): worker pooling for account proofs #18901, perf(tree): worker pooling for storage in multiproof generation #18887

[0xKarl98]

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