jobs: switch from DelayedJob to GoodJob.

Switch the ActiveJob backend from DelayedJob to GoodJob. Differences:

* The job worker is run with `bin/good_job start` instead of `bin/delayed_job`.
* Jobs have an 8 hour timeout instead of a 4 hour timeout.
* Jobs don't automatically retry on failure.
* Finishing jobs are preserved and pruned after 7 days.

db/populate.rb

@@ -1,7 +1,6 @@
 require 'set'
 
 CurrentUser.ip_addr = "127.0.0.1"
-Delayed::Worker.delay_jobs = false
 used_names = Set.new([""])
 
 def rand_string(n, unique = false)