MDL-81698 phpunit: Apply various fixes towards 1by1 execution

The changes here are heterogeneous:
- Include stuff that is not available (other test has included it).
  Sometimes local to a unit test, others in setupBeforeClass() or
  globally, ... depends on every case.
- Rename some tests (namespaces, test name, ...) towards getting it
  running.
- Amend small bits here and there.

Important note: I've left any "cosmetic" warning out from the
changes, only a few errors (like long array syntax) have been fixed.

lib/tests/task/logging_test.php

@@ -485,7 +485,7 @@ class logging_test extends \advanced_testcase {
 
         // Note PHPUnit does not support mocking static functions.
         $CFG->task_log_class = logging_test_mocked_logger::class;
-        logging_test_mocked_logger::test_reset();
+        logging_test_mocked_logger::reset_test();
 
         return $CFG->task_log_class;
     }
@@ -533,7 +533,7 @@ class logging_test_mocked_logger implements task_logger {
     /**
      * Reset the test class.
      */
-    public static function test_reset() {
+    public static function reset_test() {
         self::$isconfigured = true;
         self::$storelogfortask = [];
         self::$haslogreport = true;