MDL-67999 core_contentbank: Add namespace to upload form

The form to upload/replace files has been moved to classes/form
(it's where it should have been added when it was created).
Besides, this class has been renamed because now, with the
namespace, contentbank and form don't need to be in the name ;-)

contentbank/classes/form/upload_files.php

@@ -14,6 +14,8 @@
 // You should have received a copy of the GNU General Public License
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
+namespace core_contentbank\form;
+
 /**
  * Upload files to content bank form
  *
@@ -21,19 +23,7 @@
  * @copyright  2020 Amaia Anabitarte <amaia@moodle.com>
  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
-
-defined('MOODLE_INTERNAL') || die();
-
-require_once("$CFG->libdir/formslib.php");
-
-/**
- * Class contentbank_files_form
- *
- * @package    core_contentbank
- * @copyright  2020 Amaia Anabitarte <amaia@moodle.com>
- * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
- */
-class contentbank_files_form extends moodleform {
+class upload_files extends \moodleform {
 
     /**
      * Add elements to this form.

contentbank/upload.php

@@ -23,7 +23,6 @@
  */
 
 require('../config.php');
-require_once("$CFG->dirroot/contentbank/files_form.php");
 
 use core\output\notification;
 
@@ -86,7 +85,8 @@ $options = array(
 );
 file_prepare_standard_filemanager($data, 'files', $options, $context, 'contentbank', 'public', 0);
 
-$mform = new contentbank_files_form(null, ['contextid' => $contextid, 'data' => $data, 'options' => $options, 'id' => $id]);
+$customdata = ['contextid' => $contextid, 'data' => $data, 'options' => $options, 'id' => $id];
+$mform = new \core_contentbank\form\upload_files(null, $customdata);
 
 $error = '';