Automatically turn off field label on ActiveField->hiddenInput()

Proposed solution for yiisoft/yii2#2990

framework/widgets/ActiveField.php

@@ -382,6 +382,7 @@ class ActiveField extends Component
      */
     public function hiddenInput($options = [])
     {
+        $this->label(false);
         $options = array_merge($this->inputOptions, $options);
         $this->adjustLabelFor($options);
         $this->parts['{input}'] = Html::activeHiddenInput($this->model, $this->attribute, $options);

tests/framework/widgets/ActiveFieldTest.php

@@ -251,6 +251,7 @@ EOD;
 EOD;
         $this->activeField->hiddenInput();
         $this->assertEquals($expectedValue, $this->activeField->parts['{input}']);
+        $this->assertEquals('', $this->activeField->parts['{label}']);
     }
 
     public function testListBox()