Improve L1 interop and add testing (consensus.mligo)

[oteku]

I think it would be a good task for both learning about deku and L1/L2 to make him "refactorize" the consensus.mligo, mainly :
rename it

About consensus.mligo:

• Move smartcontract from src/tezos_interop/ to layer1/bridge
  => to have clean separation btw L1 interop and L2 interop, i would like to have only deku L2 in src/
  => It's ratger a bridge than a consensus so we put a more meaningful name

• Split the contract in modules
  => easier reading / maintenance; take ligolangs https://github.com/ligolang/advisor-cameligo or any cameligo template as architecture exemple

• Add unit & mutation tests with ligo framework

• Add contract metadata (read TZIP-12)

• Adapt every script / e2e tests