MDL-75777 phpunit: Move tests to use correct names and ns (take#6)

Applied the following changes to various testcase classes:

- Namespaced with component[\level2-API]
- Moved to level2-API subdirectory when required.
- Fixed incorrect use statements with leading backslash.
- Remove file phpdoc block
- Remove MOODLE_INTERNAL if not needed.
- Changed code to point to global scope when needed.
- Fix some relative paths and comments here and there.
- All them passing individually.
- Complete runs passing too.

question/tests/importexport_test.php

@@ -17,12 +17,15 @@
 /**
  * Unit tests for the question import and export system.
  *
- * @package    moodlecore
- * @subpackage questionbank
+ * @package    core_question
+ * @category   test
  * @copyright  2009 The Open University
  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 
+namespace core_question;
+
+use qformat_default;
 
 defined('MOODLE_INTERNAL') || die();
 
@@ -30,7 +33,6 @@ global $CFG;
 require_once($CFG->libdir . '/questionlib.php');
 require_once($CFG->dirroot . '/question/format.php');
 
-
 /**
  * Subclass to make it easier to test qformat_default.
  *
@@ -47,14 +49,13 @@ class testable_qformat extends qformat_default {
     }
 }
 
-
 /**
  * Unit tests for the matching question definition class.
  *
  * @copyright  2009 The Open University
  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
-class qformat_default_test extends advanced_testcase {
+class importexport_test extends \advanced_testcase {
     public function test_assemble_category_path() {
         $format = new testable_qformat();
         $pathsections = [