Proposal to add EIP-3670 to Shanghai

[axic]

This is an early indication to seek inclusion of EIP-3670 (EOF - Code Validation) into Shanghai.

This is connected to #329 and ideally EIP-3540 and EIP-3670 should be introduced at the same time. We did separate these into two EIPs to have reduced complexity in both specifications. It could be merged into one should that be the sentiment from ACD.

[timbeiko]

On ACD131 we decided to move this EIP to CFI for Shanghai. Closing this issue for now. We can reopen if, for whatever reasons, issues arise about the EIP's inclusion in the upgrade.