Propagate the Scroll base fee computation to the RPC

[greged93]

Describe the feature

The base fee is currently computed using the Scroll base fee function only during block building and in maintain_transaction_pool. This should also be done for gas related RPC calls.

Additional context

No response

[greged93]

Partially implemented in #291

[frisitano]

@yiweichi can you review what is oustanding here following merge of #291