Make Custom menus scrollable

Fixes arduino#11416

The patch on MenuScroller.java is needed to avoid a clash between custom menus with the same label.
This behaviour artificially increases the amount of objects that the scroller will calculate.
Eg. if two boards share the same custom menu, that menu will contain the properties for both the boards (since it's parsed twice).

app/src/processing/app/Base.java

@@ -1473,6 +1473,7 @@ public void actionPerformed(ActionEvent actionevent) {
           customMenu.putClientProperty("platform", getPlatformUniqueId(targetPlatform));
           customMenu.putClientProperty("removeOnWindowDeactivation", true);
           boardsCustomMenus.add(customMenu);
+          MenuScroller.setScrollerFor(customMenu);
         }
       }
     }

app/src/processing/app/tools/MenuScroller.java

@@ -16,6 +16,7 @@
 import java.awt.event.MouseWheelEvent;
 import java.awt.event.MouseWheelListener;
 import java.awt.event.KeyEvent;
+import java.util.Arrays;
 
 /**
  * A class that provides scrolling capabilities to a long menu dropdown or
@@ -539,7 +540,7 @@ public void popupMenuCanceled(PopupMenuEvent e) {
     }
 
     private void setMenuItems() {
-      menuItems = menu.getComponents();
+      menuItems = Arrays.stream(menu.getComponents()).filter(x -> x.isVisible()).toArray(Component[]::new);
       if (keepVisibleIndex >= topFixedCount
         && keepVisibleIndex <= menuItems.length - bottomFixedCount
         && (keepVisibleIndex > firstIndex + scrollCount