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.

lib/phpunit/tests/phpunit_dataset_test.php

@@ -80,7 +80,7 @@ class phpunit_dataset_test extends advanced_testcase {
     /**
      * test_from_file() data provider.
      */
-    public function from_file_provider() {
+    public static function from_file_provider(): array {
         // Create an unreadable file with vfsStream.
         $vfsfile = vfsStream::newFile('unreadable', 0222);
         vfsStream::setup('root')->addChild($vfsfile);
@@ -177,7 +177,7 @@ class phpunit_dataset_test extends advanced_testcase {
     /**
      * test_from_string() data provider.
      */
-    public function from_string_provider() {
+    public static function from_string_provider(): array {
 
         return [
             'wrong type' => [
@@ -267,7 +267,7 @@ class phpunit_dataset_test extends advanced_testcase {
     /**
      * test_from_array() data provider.
      */
-    public function from_array_provider() {
+    public static function from_array_provider(): array {
         return [
             'repeated array table many structures' => [
                 'structure' => [
@@ -413,7 +413,7 @@ class phpunit_dataset_test extends advanced_testcase {
     /**
      * test_load_csv() data provider.
      */
-    public function load_csv_provider() {
+    public static function load_csv_provider(): array {
 
         return [
             'repeated csv table many files' => [
@@ -501,7 +501,7 @@ class phpunit_dataset_test extends advanced_testcase {
     /**
      * test_load_xml() data provider.
      */
-    public function load_xml_provider() {
+    public static function load_xml_provider(): array {
 
         return [
             'repeated xml table multiple files' => [
@@ -669,7 +669,7 @@ class phpunit_dataset_test extends advanced_testcase {
     /**
      * test_to_database() data provider.
      */
-    public function to_database_provider() {
+    public static function to_database_provider(): array {
 
         return [
             'wrong table requested' => [
@@ -824,7 +824,7 @@ class phpunit_dataset_test extends advanced_testcase {
     /**
      * test_get_rows() data provider.
      */
-    public function get_rows_provider() {
+    public static function get_rows_provider(): array {
 
         return [
             'wrong table requested' => [