Remove 'journal_type' argument from the CLI

Motivation:

• This simplifies the CLI, and stops leaking implementation details (what field the implementation reads, what keys contains, that keys exist at all, etc.) through this interface.

• It also removes the need to have two clients, both reading revisions and releases.

This preserves the optimization of not deserializing unneeded values,
by passing raw message values to the worker functions; which can
deserialize it themselves if needed.

Additionally, this commit fixes some mistakes in type annotations.