This PR contains very small EIP-4844 additions. GasPool is modified and
now it is a struct with 2 fields "gas" and "dataGas" (blobs are priced
in dataGas). ExcessDataGas block header field added. ExcessDataGas
needed to compute the data gas price. EIP-4844 helper functions are
added as well.
This removes the burden on a single object to take care of all
validation and state processing. Now instead the validation is done by
the `core.BlockValidator` (`types.Validator`) that takes care of both
header and uncle validation through the `ValidateBlock` method and state
validation through the `ValidateState` method. The state processing is
done by a new object `core.StateProcessor` (`types.Processor`) and
accepts a new state as input and uses that to process the given block's
transactions (and uncles for rewords) to calculate the state root for
the next block (P_n + 1).