Fix fatal error (undefined function drupal_get_path) in D10

Problem/Motivation

Vartheme can be installed in D10, but is not usable because of the fatal error on every page where the theme is used:

PHP Error: Call to undefined function drupal_get_path() in vartheme_preprocess_page() (line 31 of vartheme.theme).

I know this theme is minimally maintained, but we need it for a smooth upgrade to fresh Drupal core and Varbase.

Proposed resolution

Change to \Drupal::service('extension.list.theme')->getPath('vartheme')

Remaining tasks

• ✅ File an issue about this project
• ✅ Addition/Change/Update/Fix to this project
• ✅ Testing to ensure no regression
• ➖ Automated unit/functional testing coverage
• ➖ Developer Documentation support on feature change/addition
• ➖ User Guide Documentation support on feature change/addition
• ➖ UX/UI designer responsibilities
• ➖ Accessibility and Readability
• ✅ Code review from 1 Varbase core team member
• ✅ Full testing and approval
• ✅ Credit contributors
• ✅ Review with the product owner
• ✅ Update Release Notes and Update Helper on new feature change/addition
• ✅ Release vartheme-8.x-6.13

Varbase update type

• ✅ No Update
• ➖ Optional Update
• ➖ Forced Update
• ➖ Forced Update if Unchanged

User interface changes

• N/A

API changes

• N/A

Data model changes

• N/A

Release notes snippet

• Issue #3409990 by pingwin4eg: Fixed fatal error (undefined function drupal_get_path) in D10