dnf5daemon: Introduce enabling repositories in Repo interface

[jan-kolarik]

Move the existing functionality of enabling and disabling of repositories from the RepoConf interface.

Drop the RepoConf interface as the remaining list functionality that is required by clients is already provided by the Repo::list.

Change the logic of commands to be strict against invalid arguments.

Add support for introduced commands in the dnf5daemon client.

Tests: rpm-software-management/ci-dnf-stack#1456.
Closes: #771.

[m-blaha]

/packit test –identifier dnf5daemon-tests

[m-blaha]

There is a small difference between what RepoConf.list() and Repo.list() do. The RepoConf interface returns contents of *.repo config files as they are - without any substitutions. OTOH Repo interface returns repositories as they are used - with variables substituted.

So from my point of view unifying all repo methods in one interface (Repo) makes sense. I'm not sure whether we need (have a user for) also RepoConf.list() functionality. But it can also be implemented in Repo interface with new names (like Repo.list_config()). Also we should unify attribute names used in Repo.list() and Repo.list_config(). Currently the former use patterns to filter repositories, the latter ids.

IIUC the original RepoConf interface was not documented so we should be able to drop it.