feat: unify pub/sub and query/reply modules

[wyfo]

[wyfo]

@Mallets @kydos @milyin

[wyfo]

I've let the core module as is for now. Maybe we should create a qos module to put QOS related things (Priority and CongestionControl for now, but maybe more later), as they are common to pub/sub and query/reply.

[wyfo]

About Encoding, I'm hesitating to put it in core with Priority and CongestionControl, but it may also be put in bytes module, as this is closely related. I think I prefer this solution now.

[Mallets]

@wyfo it would be great if this PR comes with a battery of sister PRs to update all bindings/plugins/backends with the new module organization.

[wyfo]

This is incredibly long to patch all backend/plugins, so I've written a Python script to modify the imports automatically 😅

[wyfo]

@Mallets All the sister PRs have been opened.