It's very easy to forget to add `require 'rails_helper'` at the top of every core/plugin spec file, and omissions can cause some very confusing/sporadic errors.
By setting this flag in `.rspec`, we can remove the need for `require 'rails_helper'` entirely.
Lots of changes but it's mostly a refactoring.
The interesting part that was fix are the 'load_problem_<model>_ids' methods.
They will now return records with no search data associated so they can be properly indexed for the search.
This "bad" state usually happens after a migration.
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
