Call eager_load! on loaded dependents, too

[rmosolgo]

Addresses the question in #5178 (comment)

This is inspired Rails's way of handling this is to hard-code dependents that should also be auto-loaded, for example: https://api.rubyonrails.org/classes/ActiveRecord.html#method-c-eager_load-21

# File activerecord/lib/active_record.rb, line 499
def self.eager_load!
  super
  ActiveRecord::Locking.eager_load!
  ActiveRecord::Scoping.eager_load!
  ActiveRecord::Associations.eager_load!
  ActiveRecord::AttributeMethods.eager_load!
  ActiveRecord::ConnectionAdapters.eager_load!
  ActiveRecord::Encryption.eager_load!
end

[rmosolgo]

I initially implemented this with recursive eager_load! calls, but given that they're hardcoded now, I'm much less worried about the scope and impact of this change.