Feature: overwrite request gas limits and return new values to relay

[prestwich]

📝 Summary

Modifies the v2 endpoint to overwrite gaslimit during simulation, and to return the overwritten values to the relay client

This allows the block-validation logic in the API to adjust the gaslimit set by the block builder in order to achieve specific gas targets specified by the relay api service.

There's some design discussion as to whether this should be a v3. I chose to make the most minimal changeset, as the goal is to have the change be transparent to block builders and proposers. As a result, this API update is not suitable for use by unmodified relay APIs

Disclaimer

I do not have confidence in my modification of the go api to return the new type

📚 References

This is in support of https://github.com/flashbots/mev-boost-relay/pull/519

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• [x] I have seen and agree to CONTRIBUTING.md

[prestwich]

hard to tell because of the large output, but given the latest commit is non-functional changes it seems likely the CI failure is unrelated