Add initial FOCIL implementation

[jihoonsong]

This PR implements initial FOCIL specifications. For more information, please refer to EIP-7805 and this PR.

[ensi321]

Pointing out Engine API has incorrect type for inclusion list. Current implementation expects base64 strings whereas the convention and the specs demand hex strings.

I suggest either define inclusion list type and its marshal type in beacon/engine/types.go and let gencodec handles the conversion similar to how ExecutableData is handled. Or manually marshal/unmarshal like how convertRequests handles incoming executionRequests in NewPayloadV4

[jihoonsong]

I've addressed comments. Thank you very much for spotting out the issue and suggesting solutions! @ensi321

[jihoonsong]

At the call with Geth team, there was feedback that eth/catalyst/api.go is not the right place to put validateInclusionListConstraints.

I haven't given much thought about where is the best location from the Geth codebase perspective, but from the spec perspective, the IL constraints should be checked after executing all transactions and before processing withdrawal requests. This is to prevent such situations that some withdrawal address become availble to cover some IL transaction that they couldn't. That missing IL transaction can reorg the block, which it shouldn't.

In current implementation, it would be between L106-L107 of core/state_processor.go.

As this would change the core part of Geth, I would wait until I can get more feedback from the Geth team before proceeding.

[jihoonsong]

This PR has been updated to validate inclusion list inside state_processor.go. Following @fjl's feedback, it puts IL transactions inside block similar to ExecutionWitness. Additionally, now it validates IL transactions before passing using it.

[jihoonsong]

This PR now has been updated to reflect the latest execution apis spec as of 2025-08-15. A Kurtosis config can access to the docker image via el_jmage: jihoonsg/geth-focil:1a1adcd