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.

search/classes/base_mod.php

@@ -293,7 +293,7 @@ abstract class base_mod extends base {
      * @param \core_search\document $doc
      * @return \core_search\document_icon
      */
-    public function get_doc_icon(document $doc) : document_icon {
+    public function get_doc_icon(document $doc): document_icon {
         return new document_icon('monologo', $this->get_module_name());
     }