Nimbus EVM isn't usable by an EVMC host
It appears that the Nimbus EVM isn't yet usable by other EVMC hosts because the execute function [here](https://github.com/status-im/nimbus-eth1/blob/94198bcf95f2d730913e933ea2f89f8c8fc57bf5/nimbus/transaction/evmc_vm_glue.nim#L19) is not implemented correctly. It casts to a nim specific type `TransactionHost` and it ignores the evmc_message and code parameters. 

It also appears that the Nimbus EVM accesses the Nimbus database directly in some places which may become a problem when running the EVM in another host.