stream: use pipe for async iterator

This is just on a prototyping stage.

I'm current of the thought that we currently use 3 different stream apis to drive streams.

I would like to reduce and unify that to one, and the one that seems to have best "compatibility" is .pipe. I'm basically proposing removing all use of .read() and 'readable' from inside core in favour of .pipe.

I believe this can be done from a behaviour perspective, however I'm very unsure it's possible with maintained performance.

I'm just opening this as a draft in case anyone have any comments or suggestions.