fix(dropdown): make "set text" work for custom actions

The set text behavior was not working for custom actions whereas such function internally calls the "set text" method.
This PR also fixes showing all items before hiding when a non-multiple dropdown allowed additions

Author: lubber-de

src/definitions/modules/dropdown.js

@@ -1413,7 +1413,9 @@
                                         module.remove.userAddition();
                                     }
                                     if (!settings.keepSearchTerm) {
-                                        module.remove.filteredItem();
+                                        if (module.is.multiple()) {
+                                            module.remove.filteredItem();
+                                        }
                                         module.remove.searchTerm();
                                     }
                                     if (!module.is.visible() && $target.length > 0) {
@@ -2587,7 +2589,7 @@
                             } else {
                                 $combo.text(text);
                             }
-                        } else if (settings.action === 'activate') {
+                        } else if (settings.action === 'activate' || isFunction(settings.action)) {
                             if (text !== module.get.placeholderText() || isNotPlaceholder) {
                                 $text.removeClass(className.placeholder);
                             }