Fixes #4374 - Nukes all (?) legacy Driver and Application stuff; revamps tests (#4376)

Tests/TerminalGuiFluentTesting/GuiTestContext.ContextMenu.cs

@@ -0,0 +1,28 @@
+#pragma warning disable CS1591 // Missing XML comment for publicly visible type or member
+
+namespace TerminalGuiFluentTesting;
+
+public partial class GuiTestContext
+{
+    /// <summary>
+    ///     Registers a right click handler on the <see cref="LastView"/> added view (or root view) that
+    ///     will open the supplied <paramref name="contextMenu"/>.
+    /// </summary>
+    /// <param name="contextMenu"></param>
+    /// <returns></returns>
+    public GuiTestContext WithContextMenu (PopoverMenu? contextMenu)
+    {
+        LastView.MouseEvent += (s, e) =>
+                               {
+                                   if (e.Flags.HasFlag (MouseFlags.Button3Clicked))
+                                   {
+                                       // Registering with the PopoverManager will ensure that the context menu is closed when the view is no longer focused
+                                       // and the context menu is disposed when it is closed.
+                                       Application.Popover?.Register (contextMenu);
+                                       contextMenu?.MakeVisible (e.ScreenPosition);
+                                   }
+                               };
+
+        return this;
+    }
+}