Run zpool trim regularly on hosts using zfs
zpool trim is a bulk operation to run DISCARD
on SSDs, which is an important operation for wear-leveling algorithms.
There's a background job which runs DISCARD on the fly, but we should do the bulk operation once in a while (e.g. every two months).
This should be far away from the automatic scrub operations to avoid cascading effects.
Migrated from T2439 (view on Phabricator)