This PR adds the `NextBaseFeePerGas` to `Block` and `EffectiveTip` to `Transaction` to make it easier for clients to compute fee history themselves via graphql queries.
* internal/ethapi/api: use hexutil.uint for blockCount parameter instead of int for feeHistory
* return hex value for oldestBlock instead of number
* return uint64 from oracle.resolveBlockRange
* eth/gasprice: fixed test
Co-authored-by: Zsolt Felfoldi <zsfelfoldi@gmail.com>