Avoid t() calls, instead use \Drupal\Core\StringTranslation\StringTranslationTrait and $this->t()

Problem/Motivation

After running coder for Drupal best practices, I found the issues regarding t() calls:

WARNING | t() calls should be avoided in classes, use \Drupal\Core\StringTranslation\StringTranslationTrait and $this->t() instead

Proposed resolution

Need to replace t() calls with $this->t() wherever required.