timers: async track unref timers

When async hooks integration for Timers was introduced, it was
not included in the code for unref'd or subsequently ref'd
timers which means those timers only have Timerwrap hooks.

PR-URL: https://github.com/nodejs/node/pull/18579


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>