Add mnemonic sentence support

[palas]

Changelog

- description: |
    Added support for mnemonic sentence generation and extended key derivation from mnemonic sentences.
  type:
  - feature

Context

This PR is associated to: IntersectMBO/cardano-api#678.
It is part of an effort to integrate cardano-addresses functionalities into the cardano-cli.

How to trust this PR

I would look mainly at the logic, the changes in the help golden files, and probably testing it is the best way.

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• New tests are added if needed and existing tests are updated. See Running tests for more details
• Self-reviewed the diff

[Jimbo4350]

LGTM but I want feedback from the rest of the team before we approve and merge.

[Jimbo4350]

I think when writing to file we should at least set restrictive permissions. Can you get in touch with the wallet team and ask them what precautions they took when generating mnemonics?

[Jimbo4350]

I am wondering if we should have a new command root-key that has these commands underneath. We need to make a clear distinction between the root key and the derived keys. Putting the commands under key makes this distinction a little less clear IMO.

[palas]

So far we are not really letting the user handle root keys, we are deriving normal extended keys directly from the mnemonic. But if we plan on adding support for deriving root keys too, and/or other commands specific for root keys then it would make sense.