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/classes/plugin_manager.php

@@ -909,7 +909,7 @@ class core_plugin_manager {
      * @param int $branch the moodle branch to check support for
      * @return string
      */
-    public function check_explicitly_supported($plugin, $branch) : string {
+    public function check_explicitly_supported($plugin, $branch): string {
         // Check for correctly formed supported.
         if (isset($plugin->pluginsupported)) {
             // Broken apart for readability.