Support JSON-RPC batch requests

[kdeme]

The JSON-RPC specification allows for batching requests and getting a response containing an array of responses for each request. See also https://www.jsonrpc.org/specification#batch

This is for example supported in geth: https://geth.ethereum.org/docs/interacting-with-geth/rpc/batch , and probably other clients.

One example where this would have been very usefyl was for eth_getTransactionReceipt. As to build the full receipts list per block, one would have to iterate over all transactions to request the individual receipts. I say would have, as this got resolved with this addition: ethereum/execution-apis#393