Feat/registry

[julienh-ssv]

This PR is a proof of concept wiring of our new compose-registry:

Feature:

• Mailboxes are fetched from the new registry
• A new optional flag is added to allow selecting the registry path (only useful for local dev environments, by default embedded registry is used)

[kchojn]

I think this is the wrong place for PR
op-geth is expected to be mostly supported by the SDK Publisher, so the whole registry part should be:

• moved to compose-publisher/publisher
  OR
• in a very minimal version in op-geth; now I see several public utils, so shouldnt they be made available via registry?