Issue #3570710 by dydave: Use autowiring for services and controllers.

https://www.drupal.org/project/admin_toolbar/issues/3570710

Use autowiring for services and controllers:

• Updated services yaml files to Add autowire: true and remove arguments.
• Updated Services and Controller class files: Added use AutowireTrait and updated constructors to autowire services.

Additional change: Moved all admin_toolbar images under a single directory:

• Git moved the image files to the images folder.
• Updated the impacted CSS files accordingly with a find and replace of the paths.