Issue #1893442 by andypost, tim.plunkett, dawehner: Move BlockStorageController::loadByProperties() into ConfigStorageController.
Issue #1970136 by dawehner, olli: Fixed Read more link isn't rendered.
Issue #1998992 by damiankloip, andypost: Typo in FieldOverview.php.
Issues #1987602, #1978894, #1978892: Migrate ajax form callbacks to controllers.

  - ajax_form_callback()
  - file_ajax_upload()
  - file_ajax_progress()
Issues #1987602, #1978894, #1978892: Fix dumb namespace error.
Issues #1987602, #1978894, #1978892: Remove file include since it's not
supported for routes and doesn't appear to be needed.