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/xapi/classes/privacy/provider.php

@@ -39,7 +39,7 @@ class provider implements
      * @param   collection $collection The initialised collection to add items to.
      * @return  collection A listing of user data stored through this system.
      */
-    public static function get_metadata(collection $collection) : collection {
+    public static function get_metadata(collection $collection): collection {
         $collection->add_database_table('xapi_states', [
                 'component' => 'privacy:metadata:component',
                 'userid' => 'privacy:metadata:userid',