feat: dynamic gas/pubdata price

[itegulov]

There are two modes of operation: from a fork and independent. Both can be improved in how they set gas/pubdata price.

Fork

Current gas and pubdata price are taken from the fork at the moment of initialization and then never change. Which makes some amount of sense since we effectively "freeze" our fork view, but perhaps it would make sense to make it more dynamic to reflect production-like fluctuation.

Independent

era-test-node has default gas settings but they can be overridden via config. Perhaps we should allow a dynamic way to manipulate gas price or maybe manipulate prod-like fee params (e.g. manually set fake time txs spend in mempool). Also just generally consider time txs spend in mempool since we have one now.