Agnostic_baker: Add run accuser command

What

This MR adds the run accuser command which should behave in the following way: if previously the accuser would use the syntax:

./octez-accuser-<proto> <GLOBAL_OPTIONS> run <ACCUSER_OPTIONS>

Now, the following has the same effect:

./octez-agnostic-baker <GLOBAL_OPTIONS> run accuser <ACCUSER_OPTIONS>

Why

Because we want the users to be able to run the accuser binary from the agnostic baker, therefore making the ./octez-accuser-<proto> binaries obsolete. Also, because of the agnostic baker mechanism, this should adapt well to the protocol migrations and UAUs. This is because, in those cases, the Lwt-mechanism from the agnostic baker will cancel the running thread (in this case the accuser), and it will start the new accuser code (which is based on the plugin of the new protocol).

How

By adding a run accuser command in the agnostic baker, which calls the code from the Client_daemon.Accuser module.

Manually testing the MR

One can test (for starters, more tests to come) with the following:

./octez-agnostic-baker --base-dir <client-dir> --endpoint <node-endpoint> run accuser

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR