fix: Do not query L1 on every request to `getCurrentBaseFees`

[spalladino]

As per title. Every time getCurrentBaseFees is hit, which is exposed in the RPC API and also called every time we need to validate a sent tx, we do multiple eth_calls to have the rollup contract compute the base fees.

We should update this value in the archiver on every new L1 (or L2?) block instead. If not possible, at least cache it based on L1 block to avoid constantly bombarding L1.