fix: serialize accessList storageKeys in camelCase per Ethereum JSON-RPC spec

[ionodeionode]

Summary

Fixes opentensor/subtensor#2143

Problem

The ethereum crate's AccessListItem struct serializes the storage_keys field in snake_case:

{
  "address": "0x9dc08c6e2bf0f1eed1e00670f80df39145529f81",
  "storage_keys": []
}

However, the Ethereum JSON-RPC specification requires camelCase (storageKeys):

{
  "address": "0x9dc08c6e2bf0f1eed1e00670f80df39145529f81",
  "storageKeys": []
}

This breaks indexers and tooling that validate against the spec. The issue was reported by the Subsquid team who encountered problems while indexing the Bittensor mainnet.

Solution

Added a custom serialization wrapper (AccessListItemCamelCase) and a serialize_with module (access_list_camelcase) for the Transaction struct's access_list field. This ensures storageKeys is serialized in the correct camelCase format without modifying the underlying ethereum crate type.

Note: The rpc-v2 types already define their own AccessListItem with #[serde(rename_all = "camelCase")], so only rpc-core is affected by this bug.

Before

curl <bittensor-rpc-endpoint> -X POST -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","method":"eth_getTransactionByHash","id":4, "params": ["0x98e15..."]}' | jq '.result.accessList'

[{ "address": "0x...", "storage_keys": [] }]

After

[{ "address": "0x...", "storageKeys": [] }]