EIP- 7843 additional test cases

[kclowes]

Some extra cases, feel free to add to this PR or the testing tracker.

1. Multi block case, where we have two blocks ("within the same slot") where block 1 and 2 do not have the same slot number.
2. Fork transition test. Check not enabled before fork and enabled after fork.

We should add a mainnet test for execute here too I think!

Originally posted by @spencer-tb in #2853 (review)