chore: Clean up report & knowledge base policies (#11234)

- Removes the portal_members table and all associated records
- Updates policies to use custom roles with knowledge_base_manage
permission
- Updates controllers, models, and views to work without portal
membership
- Adds tests for the new permission model

app/policies/article_policy.rb

@@ -1,37 +1,31 @@
 class ArticlePolicy < ApplicationPolicy
   def index?
-    @account_user.administrator? || @account.users.include?(@user)
+    @account.users.include?(@user)
   end
 
   def update?
-    @account_user.administrator? || portal_member?
+    @account_user.administrator?
   end
 
   def show?
-    @account_user.administrator? || portal_member?
+    @account_user.administrator?
   end
 
   def edit?
-    @account_user.administrator? || portal_member?
+    @account_user.administrator?
   end
 
   def create?
-    @account_user.administrator? || portal_member?
+    @account_user.administrator?
   end
 
   def destroy?
-    @account_user.administrator? || portal_member?
+    @account_user.administrator?
   end
 
   def reorder?
-    @account_user.administrator? || portal_member?
-  end
-
-  private
-
-  def portal_member?
-    @record.first.portal.members.include?(@user)
+    @account_user.administrator?
   end
 end
 
-ArticlePolicy.prepend_mod_with('Enterprise::ArticlePolicy')
+ArticlePolicy.prepend_mod_with('ArticlePolicy')