When we run the S3 inventory, mark uploads that exist as verified true, those that don't as verified false, and uploads not included in the check / not yet checked as verified nil.
This is a very expensive process, and it should only be required in exceptional circumstances. It is possible to run a similar recovery using `rake uploads:recover` (5284d41a8e/lib/upload_recovery.rb (L135-L184))
When we change upload's sha1 (e.g. when resizing images) it won't match the data in the most recent S3 inventory index. With this change the uploads that have been updated since the inventory has been generated are ignored.
This change both speeds up specs (less strings to allocate) and helps catch
cases where methods in Discourse are mutating inputs.
Overall we will be migrating everything to use #frozen_string_literal: true
it will take a while, but this is the first and safest move in this direction
