$this->t() should be used instead of t() for Drupal 8 version

Needs re-roll.

After reviewing the patch, I think that this issue can be closed because the patch contains changes using the object context for static functions, I also reviewed the t()/$this->t() calls in other files and made sure that the translation function was applied correctly to other calls

I think these have all been fixed, such as by #2948324: Fix Drupal best practices in code → . If not, please re-open and use an issue fork and merge request.