Implement a publisher with the `n2c Local Message Submission` mini-protocol with Pallas

[jpraynaud]

Why

We need to implement a message publisher in the signer which relies on the n2c Local Message Submission mini-protocol implementation in the Pallas library.

What

Implement a publisher with the n2c Local Message Submission mini-protocol implementation in the Pallas library.

How

• Implement a message publisher with Pallas in the signer
• Implement a KES signer/verifier abstraction in the message publisher to create KES signature and retrieve OpCert
• Add optional configuration for DMQ node in the signer
• Wire the DMQ publsiher in the DI