backwards_navigation displays always allowed in quiz_config_overview

Problem/Motivation

Whatever the value of backwards_navigation is in quiz settings, the overview displays "Allowed". The same is produced with "time_limit" which is never empty.

Steps to reproduce

Play with the backwards_navigation value and then display the quiz.

Proposed resolution

The problem comes from QuizViewBuilder around line 165

    $stats[] = [
      ['header' => TRUE, 'data' => $this->t('Backwards navigation')],
      $quiz->get('backwards_navigation') ? $this->t('Allowed') : $this->t('Forbidden'),
    ];

$quiz->get('backwards_navigation') should be $quiz->get('backwards_navigation')->value

    if (!$quiz->get('time_limit')->isEmpty()) {
      $stats[] = [
        ['header' => TRUE, 'data' => $this->t('Time limit')],
        _quiz_format_duration($quiz->get('time_limit')->value),
      ];
    }

The test should be on the value if ($quiz->get('time_limit')->value) not on the field.

Remaining tasks

User interface changes

API changes

Data model changes