Use `hexutil.Uint` for `blockCount` parameter in `feeHistory` method (#23239)

* 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>