Mainnet configuration values missing from API spec output
The following values are present in the `configs/mainnet.yaml` file in the Ethereum consensus specs, but are not provided in the nimbus output of the `/eth/v1/config/spec` endpoint:

- MAX_PAYLOAD_SIZE
- BLOB_SIDECAR_SUBNET_COUNT_ELECTRA
- MAX_REQUEST_BLOB_SIDECARS_ELECTRA

(Note that this does not cover post-Electra values.)

Reference https://github.com/ethereum/beacon-APIs/issues/510