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.

course/classes/search/section.php

@@ -202,7 +202,7 @@ class section extends \core_search\base {
      * @param \core_search\document $doc
      * @return \core_search\document_icon
      */
-    public function get_doc_icon(\core_search\document $doc) : \core_search\document_icon {
+    public function get_doc_icon(\core_search\document $doc): \core_search\document_icon {
         return new \core_search\document_icon('i/section');
     }