[incfs] Space trimming for IncFS v1

Run a manual timed job that trims all files one by one on the
old version of IncFS, where it didn't do it automatically.

Bug: 183435580
Fixes: 183436717
Test: atest libincfs-test service.incremental_test
Change-Id: I57885b2826e383814822c767802f837135fd8464