MDL-78159 lib: Added missing properties for core libraries

In PHP 8.2 and later, setting a value to an undeclared class property is
deprecated and emits a deprecation notice.
So we need to add missing class properties that still need to be declared.

lib/outputcomponents.php

@@ -1116,6 +1116,9 @@ class single_select implements renderable, templatable {
      */
     var $helpicon = null;
 
+    /** @var component_action[] component action. */
+    public $actions = [];
+
     /**
      * Constructor
      * @param moodle_url $url form action target, includes hidden fields
@@ -2866,6 +2869,9 @@ class html_table {
     /** @var bool Whether to make the table to be scrolled horizontally with ease. Make table responsive across all viewports. */
     public $responsive = true;
 
+    /** @var string class name to add to this html table. */
+    public $class;
+
     /**
      * Constructor
      */