Clean up the namespacing for sub-behaviors deps p2p code

[MitchTurner]

We have a mixed notation for importing and using events and behaviors from sub-behavior crates:

For example, we import the Kademlia:

use libp2p::{
    request_response::{
        Behaviour as RequestResponse,
        Config as RequestResponseConfig,
        Event as RequestResponseEvent,
    },
};

where it would probably be cleaner to import as:

use libp2p::request_response;

and then use like this:

request_response::Event;

or

request_response::Behaviour;

etc