DEV: Convert min_trust_to_edit_post to groups (#24840)

We're changing the implementation of trust levels to use groups. Part of this is to have site settings that reference trust levels use groups instead. It converts the min_trust_to_edit_post site setting to edit_post_allowed_groups.

The old implementation will co-exist for a short period while I update any references in plugins and themes.

app/models/concerns/limited_edit.rb

@@ -4,13 +4,22 @@ module LimitedEdit
   extend ActiveSupport::Concern
 
   def edit_time_limit_expired?(user)
-    return true if user.trust_level < SiteSetting.min_trust_to_edit_post
+    return true if !trusted_with_edits?(user)
     time_limit = user_time_limit(user)
     created_at && (time_limit > 0) && (created_at < time_limit.minutes.ago)
   end
 
   private
 
+  # TODO: This duplicates some functionality from PostGuardian. This should
+  #       probably be checked there instead, because this has nothing to do
+  #       with time limits.
+  #
+  def trusted_with_edits?(user)
+    user.trust_level >= SiteSetting.min_trust_to_edit_post ||
+      user.in_any_groups?(SiteSetting.edit_post_allowed_groups_map)
+  end
+
   def user_time_limit(user)
     if user.trust_level < 2
       SiteSetting.post_edit_time_limit.to_i