Move gas refund calculation from MainnetTransactionProcessor to GasCalculator

[daniellehrner]

PR description

Because of EIP-7623 the gas refund calculation will change with the upcoming Prague hard fork. Right now this calculation is hardcoded in MainnetTransactionProcessor. This PR moves this calculation to the GasCalculator, which allows to change the refund calculation with a new hardfork.

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Locally, you can run these tests to catch failures early:

• unit tests: ./gradlew build
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• integration tests: ./gradlew integrationTest
• reference tests: ./gradlew ethereum:referenceTests:referenceTests

[siladu]

Some minor comments.

I have spiked out the complete EIP-7623 and tested against devnet5 spec tests in this PR: #8117

[siladu]

There's already several pieces of refund logic scattered across the GasCalculators, most recently calculateDelegateCodeGasRefund.

I think it's confusing to have refund logic both in RefundCalculator classes and in the GasCalculator classes, would prefer one or the other.

I have a slight preference for putting this logic into the GasCalculator classes since it's a smaller change than extracting all the other refund logic.

Won't block the PR on it.

[siladu]

Alternatively, if it makes sense to make this a very precise type of RefundCalculator with a precise name, then maybe it works. Not sure what that name would be and if this is sufficiently isolated enough from the other refund logic.

[daniellehrner]

@siladu I think you are right, I've moved the logic to the GasCalculator and got rid of the RefundCalculator

[siladu]

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