In development, classes are lazy loaded so `Jobs::Onceoff.onceoff_job_klasses`
may not have been set. This is not a problem in production cause stuff
is eager loaded.
Follow-up to f4d06f195d
We are investigating a memory leak in Sidekiq and saw the following line
when comparing heap dumps over time.
`Allocated IMEMO 14775 objects of size 591000/7389528 (in bytes) at:
/var/www/discourse/app/jobs/onceoff/onceoff.rb:36`
That line in question was doing a `.select { |klass| klass < self }` on
`ObjectSpace.each_object(Class)`. This for some reason is allocating a
whole bunch of `IMEMO` objects which are instruction sequence objects.
Instead of diving deeper into why this might be leaking, we can just
save our time by switching to an implementation that is more efficient
and does not require looping through a ton of objects.
Zeitwerk simplifies working with dependencies in dev and makes it easier reloading class chains.
We no longer need to use Rails "require_dependency" anywhere and instead can just use standard
Ruby patterns to require files.
This is a far reaching change and we expect some followups here.
