MDL-65292 style: Fix all function declarations white space

This has been generated running the following Sniffs, all
them part of the Moodle's CodeSniffer standard:
- PSR12.Functions.ReturnTypeDeclaration
- PSR12.Functions.NullableTypeDeclaration
- moodle.Methods.MethodDeclarationSpacing
- Squiz.Whitespace.ScopeKeywordSpacing

All them are, exclusively, about correct spacing, so the changes
are, all them, only white space changes.

Only exceptions to the above are 3 changes what were setting the
return type in a new line, and, when that happens, the closing
parenthesis (bracket) has to go to the same line than the colon.

lib/xapi/tests/external/post_statement_test.php

@@ -187,7 +187,7 @@ class post_statement_test extends externallib_advanced_testcase {
      *
      * @return  array
      */
-    public function components_provider() : array {
+    public function components_provider(): array {
         return [
             'Inexistent component' => [
                 'inexistent_component', []
@@ -233,7 +233,7 @@ class post_statement_test extends externallib_advanced_testcase {
      *
      * @return  array
      */
-    public function invalid_json_provider() : array {
+    public function invalid_json_provider(): array {
         return [
             'Wrong json' => [
                 'This is not { a json object /'
@@ -376,7 +376,7 @@ class post_statement_test extends externallib_advanced_testcase {
      *
      * @return  array
      */
-    public function statement_provider() : array {
+    public function statement_provider(): array {
         return [
             // Single statement with group statements enabled.
             'Single, Valid actor, valid verb' => [
@@ -449,7 +449,7 @@ class post_statement_test extends externallib_advanced_testcase {
      *
      * @return  array
      */
-    public function group_statement_provider() : array {
+    public function group_statement_provider(): array {
         return [
             // Single statement with group statements enabled.
             'Group statement + group statement without group support' => [