MDL-73348 phpunit: normalize all privacy provider tests

As far as now all them have correct privacy level2 namespace:
- Move them to "privacy" subdir.
- Rename the files to "provider_test.php", this includes old
  privacy_test.php and privacy_provider_test.php files
- Rename the testcase to provider_test too (to match file name)

Also, change some relative paths and comments to point to new
locations.

mod/workshop/allocation/manual/tests/privacy/provider_test.php

@@ -15,7 +15,7 @@
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
 /**
- * Provides the {@link workshopallocation_manual_privacy_provider_testcase} class.
+ * Provides the {@see workshopallocation_manual\privacy\provider_test} class.
  *
  * @package     workshopallocation_manual
  * @category    test
@@ -34,7 +34,7 @@ defined('MOODLE_INTERNAL') || die();
  * @copyright 2018 David Mudrák <david@moodle.com>
  * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
-class privacy_provider_test extends \core_privacy\tests\provider_testcase {
+class provider_test extends \core_privacy\tests\provider_testcase {
 
     /**
      * When no preference exists, there should be no export.