Port ToolStripCollectionEditor to the Runtime (#12896)

Author: LeafShi1

src/System.Design/src/System.Design.Forwards.cs

@@ -83,6 +83,7 @@
 [assembly: TypeForwardedTo(typeof(System.Windows.Forms.Design.ToolStripMenuItemDesigner))]
 [assembly: TypeForwardedTo(typeof(System.Windows.Forms.Design.TrackBarDesigner))]
 [assembly: TypeForwardedTo(typeof(System.Windows.Forms.Design.TreeViewDesigner))]
+[assembly: TypeForwardedTo(typeof(System.Windows.Forms.Design.ToolStripCollectionEditor))]
 [assembly: TypeForwardedTo(typeof(System.Windows.Forms.Design.UpDownBaseDesigner))]
 [assembly: TypeForwardedTo(typeof(System.Windows.Forms.Design.UserControlDocumentDesigner))]
 

src/System.Windows.Forms.Design/src/Resources/SR.resx

@@ -1476,6 +1476,12 @@ Press Ctrl+Enter to accept Text.</value>
   <data name="TableLayoutPanelSpanDesc" xml:space="preserve">
     <value>TableLayoutPanel cannot expand to contain the control, because the panel's GrowStyle property is set to 'FixedSize'.</value>
   </data>
+  <data name="ToolStripItemCollectionEditorLabelNone" xml:space="preserve">
+    <value>(&amp;None)</value>
+  </data>
+  <data name="ToolStripItemCollectionEditorLabelMultipleItems" xml:space="preserve">
+    <value>(&amp;Multiple Items)</value>
+  </data>
   <data name="ImageListActionList_ChooseImagesDescription" xml:space="preserve">
     <value>Opens the Images collection editor</value>
   </data>