Add Electra fork boilerplate

[macladson]

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Proposed Changes

Since I have been involved with the Verkle-enabled implementation of Lighthouse (which I had optimistically been calling "Electra"), and with it becoming increasingly unlikely that Verkle trees will end up in Electra, I figured I would rip out all of the Verkle related code and just leave the Electra fork skeleton.

People can use this branch as a base for any Electra-related PRs so they don't need to write the Fork impl themselves. Once this is merged, it should allow us to split the upcoming work for Electra into smaller PRs.

Additional Information

This should cover most of the existing tests, but I may have missed a few things. It excludes the EF spec tests for now, since none exist, these will need to be manually enabled once they are available.

There are a few other TODO(electra)'s but many of them should generate compile-time errors once actual features are added to the fork.

There are also some improvements to lcli.

[michaelsproul]

I'm in favour of merging this ASAP so we don't need a long-lived branch!

[dapplion]

@macladson can you cherry-pick this commit? I have fixed conflicts with unstable, mainly adding the new lightclient fork-types

https://github.com/dapplion/lighthouse/commit/21dadec42a63606db9267ea315af1a7daca265aa

[realbigsean]

@mergifyio queue

[mergify[bot]]

queue

✅ The pull request has been merged automatically

The pull request has been merged automatically at f8fdb71f50851bf7792e68a4ee31125bd645e19a