There is currently no way for JSON-RPC clients to discover which
historical data a node can serve without probing with trial-and-error
calls and interpreting opaque error messages (`pruned history
unavailable`).
This makes it hard to build robust tooling on top of nodes that prune
their history, for example nodes started with `--history.chain
postmerge`
or with reduced `TransactionHistory`, `LogHistory`, or `StateHistory`
windows.
This PR implements `eth_capabilities` as defined in
ethereum/execution-apis#755. The method takes no parameters and returns
the current head plus six per-resource capability records:
- `state`
- `tx`
- `logs`
- `receipts`
- `blocks`
- `stateproofs`
Closes#33828
