Consider putting the CLI in a separate python package

[llucax]

What's needed?

It doesn't seem to be nice to pollute the "library namespace" with the CLI stuff.

Proposed solution

We could have a src/frequenz/client/dispatch/cli/__init__.py, src/frequenz/client/dispatch/cli/_main.py and src/frequenz/client/dispatch/cli/_types.py for example.

Use cases

No response

Alternatives and workarounds

No response

Additional context

We should consider even to eventually I would like to ship it as a separate pip package (frequenz-client-dispatch-cli)