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/check/manager.php

@@ -62,7 +62,7 @@ class manager {
      *
      * @return array of check objects
      */
-    static public function get_performance_checks() : array {
+    static public function get_performance_checks(): array {
         $checks = [
             new performance\designermode(),
             new performance\cachejs(),