eip-7918: blob base fee bounded by execution cost

[anvacaru]

This PR implements EIP-7918, which introduces a reserve price mechanism for the blob base fee to ensure proper fee market functioning and fair pricing for blob verification compute costs.

• Modified Cexcessblob to accept a 4th parameter (BASE_FEE) for reserve price calculation, representing the base fee of the parent block. Rules have been updated to follow this logic:

def calc_excess_blob_gas(parent: Header) -> int:
    target_blob_gas = GAS_PER_BLOB * blobSchedule.target
    if parent.excess_blob_gas + parent.blob_gas_used < target_blob_gas:
        return 0

    if BLOB_BASE_COST * parent.base_fee_per_gas > GAS_PER_BLOB * get_base_fee_per_blob_gas(parent):
        return parent.excess_blob_gas + parent.blob_gas_used * (blobSchedule.max - blobSchedule.target) // blobSchedule.max
    else:
        return parent.excess_blob_gas + parent.blob_gas_used - target_blob_gas

• A new previousBaseFee cell has been added to track the base fee of the parent block.