This PR ties lots of loose ends in asyncio

[arhadthedev]

This PR ties lots of loose ends in asyncio so it becomes clear what is a callback (a reaction shat shouldn't be called) and what is a proper function (an action that needs to be called):

• for transports, it replaced self._protocol with ... to ...

In other words, currently a caller takes a callie and sticks into it each time a call in required, and after this PR a caller just calls its self._on_* without knowing about a callie that subscribed once on its creation.