add gas refund handler to refund the remaining gas fee at the end of transaction

[AaronZgl]

Description

add the gas refund handler to refund the remaining gas fee at the end of transaction.

closes: #2150

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[fdymylja]

@AaronZgl, from my reading of your code, I understand that in case gas provided is 1000 and gas used is 100, then you refund the 900 gas fully.

Now if this is the case, I'd suggest you to give a read to #2150 and how refunding the whole amount can provide a dos attack vector.

[fdymylja]

On a side note, probably it'd make sense to provide the option to set a custom gas refund handler if we agree that this is something that happens after each TX is processed (in the linked issue there were proposals to handle this at endblock level), to allow devs to inject their own custom gas handlers.

But I wouldn't support adding a default gas refund handler mechanism until a spec is written and there is consensus around that.

[alessio]

Blocking as per #8993 (comment)

[tac0turtle]

@AaronZgl Thank you for taking this on. We are all excited for such a feature to land. Like @fdymylja mentioned we would want a spec or ADR to flesh out the design before the implementation can be merged. Could you write such a document, I can help push it along by getting all the required parties involved.

[AaronZgl]

@AaronZgl, from my reading of your code, I understand that in case gas provided is 1000 and gas used is 100, then you refund the 900 gas fully.

Now if this is the case, I'd suggest you to give a read to #2150 and how refunding the whole amount can provide a dos attack vector.

If block gas limit is set to infinity, dos attack can be avoided, block gas limit can be limited by transaction gas limt and transaction quantity

[amaury1093]

@AaronZgl are you planning to write an ADR for this?

[tac0turtle]

@AaronZgl I'm closing this PR. Let's write an ADR for a design, and then we can reopen this PR.