quic: refactor qlog handling

Because of the timing of qlog events emitted by ngtcp2, it
becomes difficult to handle those as events on the QuicSession
object because the final qlog entry is not emitted until the
ngtcp2_conn is freed, which can occur when the object is being
garbage collected (meaning, we a: can't call out to javascript
and b: don't have an object we can use to emit the event).

This refactors it into a QLogStream object that allows the
qlog data to be piped out using a separate Readable stream.

PR-URL: https://github.com/nodejs/node/pull/34160


Reviewed-By: Anna Henningsen <anna@addaleax.net>