feat: adjustable gas price

[Autoparallel]

Idea

To make simulations as realistic as possible, we need to give agents some raw ether and force them to pay gas for transactions. At the moment, the gas price has been fixed to zero.

Solution

We can set another parameter in EnvironmentParameters similar to how I commented on #418. We can have an enum, or something, that allows the user to choose some gas rules for the environment. They can be externalized, stochastic, or off, e.g.,:

pub enum GasRules {
     UserControlled,
     Randomized(f64),
     None(u128),
}

• UserControlled: will give the user the ability to make calls such as client.set_gas_price().
• Randomized: would give the user gas price based on something like EIP-1559 rules. Could even play off of the BlockType enum I mentioned in #418.
• None: The user would not change gas price ever and have it set to the internal u128.

This GasRules can go into the EnvironmentParameters.

We can also perhaps add functionality for gas tips later on if we expand upon an enum.

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IT IS WORTH NOTING THAT ISSUE #410 IS RELEVANT HERE TOO

[Autoparallel]

I am going to work on this soon. I have thoughts on how to get a basic version of this done.

[0xJepsen]

We could probably put this in an arbiter.toml that would maybe configure revm?