pool/rpc: User operation cache

[dancoombs]

Describe the feature Add an in-memory cache of user operations for use in eth_getUserOperationByHash and eth_getUserOperationReceipt such that these API methods can be served locally in the bundler vs needing to query the node. Can keep a cache of N blocks and if we miss, can query the node. This will increase latency on calls for historical data, so it should be carefully considered.

Taken to its extreme, we could provide a full cache database on the Rundler node of all UOs. Nodes would sync with the chain and then write to the DB with each block.

[github-actions[bot]]

This issue is stale because it has been open 30 days with no activity. Remove stale label or comment or this will be closed in 5 days.