http: define all used properties in constructors

Adding all used properties in the constructor makes the hidden class
stable and heap snapshots more verbose.

Refs: https://github.com/nodejs/node/issues/8912
PR-URL: https://github.com/nodejs/node/pull/9116


Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>