Extracts session and stream from quic/core.js

[rickyes]

Extract session and stream in quic/core.js to make the code easier to read.

refer to #33928.

[jasnell]

This is fine, but please hold off on doing this. The javascript code is going to be seeing a major refactoring within the next couple weeks that I've already started.

[jasnell]

Closing as no longer relevant since the quic bits were removed.