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.

auth/oauth2/classes/auth.php

@@ -631,7 +631,7 @@ class auth extends \auth_plugin_base {
      * @param stdClass $user A user object
      * @return string[] An array of strings with keys subject and message
      */
-    public function get_password_change_info(stdClass $user) : array {
+    public function get_password_change_info(stdClass $user): array {
         $site = get_site();
 
         $data = new stdClass();