API Move some code to framework to be reusable (#3022)

Some of this code needs to be usable on classes other than SiteTree with
the CMSMain refactoring.

code/Controllers/CMSMain.php

@@ -1064,6 +1064,8 @@ public function Breadcrumbs($unlinked = false)
                 if ($page = SiteTree::get()->byID($parentID)) {
                     $this->buildListViewBreadcrumb($items, $page);
                 }
+                // At this stage we also know the parent ID is the "current" ID for this view
+                $this->setCurrentPageID($parentID);
             }
         }
 

code/Model/RedirectorPage.php

@@ -21,11 +21,6 @@
  */
 class RedirectorPage extends Page
 {
-    /**
-     * @deprecated 5.4.0 use class_description instead.
-     */
-    private static $description = 'Redirects requests to another location';
-
     private static string $class_description = 'Redirects requests to another location';
 
     private static $icon_class = 'font-icon-p-redirect';