timers: re-enter C++ less frequently

Pass in Timer.now() as an argument of kOnTimeout instead of always
re-entering C++ to get it. Also don't constantly call Timer.now()
from ontimeout, even when it isn't needed. Improves performance
on our pooled benchmark by upwards of 40%.

PR-URL: https://github.com/nodejs/node/pull/18486


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>