genesis validation exceptions

[bitwiseguy]

There are few chains (celo, boba) that skip the genesis validation in scr because they have non-standard genesis files. op-geth also has to hardcode these exceptions (ref). Other execution clients would have to do the same.

This could be improved and only require hardcoding or flagging the exception in one place, ideally in the scr (e.g. in the chain's config file, which all execution clients could inspect to know if they should process the genesis file