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.

group/group_form.php

@@ -41,7 +41,7 @@ class group_form extends moodleform {
     /**
      * Definition of the form
      */
-    function definition () {
+    function definition() {
         global $USER, $CFG, $COURSE;
         $coursecontext = context_course::instance($COURSE->id);