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.

admin/renderer.php

@@ -617,7 +617,7 @@ class core_admin_renderer extends plugin_renderer_base {
      * @param bool $croninfrequent
      * @return string HTML to output.
      */
-    public function cron_infrequent_warning(bool $croninfrequent) : string {
+    public function cron_infrequent_warning(bool $croninfrequent): string {
         global $CFG;
 
         if (!$croninfrequent) {