MDL-81521 core: Update all possibly data providers to be static

Note: Some data providers could not be automatically be converted to
being static. These will be handled in a separate issue.

mod/data/tests/lib_test.php

@@ -746,7 +746,7 @@ class lib_test extends \advanced_testcase {
      *
      * @return array
      */
-    public function data_get_config_provider() {
+    public static function data_get_config_provider(): array {
         $initialdata = (object) [
             'template_foo' => true,
             'template_bar' => false,
@@ -837,7 +837,7 @@ class lib_test extends \advanced_testcase {
      *
      * @return array
      */
-    public function data_set_config_provider() {
+    public static function data_set_config_provider(): array {
         $basevalue = (object) ['id' => rand(1, 1000)];
         $config = [
             'template_foo'  => true,