Usage of removed/depracated 'drupal_get_path' function

Problem/Motivation

Inside the FontAwesomeManager class, the drupal_get_path function is used, which is deprecated in Drupal 9 and removed in Drupal 10.

Steps to reproduce

• Add a fontawesome field on any entity type
• Create a new entity (the one with the fontawesome field) and fill the field
• Try to save the entity

I tried this on a taxonomy term and a node and on both entity types I get the error:

Error: Call to undefined function Drupal\fontawesome\drupal_get_path() in Drupal\fontawesome\FontAwesomeManager->getMetadataFilepath() (line 304 of modules/contrib/fontawesome/src/FontAwesomeManager.php).

Proposed resolution

We should replace the drupal_get_path function with the extionsion.list.module service.

\Drupal::service('extension.list.module')->getPath('fontawesome')