[EXPLORER][SHELL32][USER32] Implement 'Show the Desktop' action of Task Bar (#668)

The keyboard shortcuts Win+D and Win+M are also enabled.

- Implement IShellDispatch4::ToggleDesktop().
- Implement some commands in CTrayWindow.
- Add "sdk/include/reactos/traycmd.h" for tray commands.
- Fix task window switching.
- Improve the user32!SwitchToThisWindow() function and use it.

CORE-14318, CORE-13157
See also: CORE-14806 and CORE-8723

base/shell/explorer/taskswnd.cpp

@@ -1582,25 +1582,13 @@ public:
 
             if (!bIsMinimized && bIsActive)
             {
-                ::PostMessage(TaskItem->hWnd,
-                    WM_SYSCOMMAND,
-                    SC_MINIMIZE,
-                    0);
+                ::ShowWindowAsync(TaskItem->hWnd, SW_MINIMIZE);
                 TRACE("Valid button clicked. App window Minimized.\n");
             }
             else
             {
-                if (bIsMinimized)
-                {
-                    ::PostMessage(TaskItem->hWnd,
-                        WM_SYSCOMMAND,
-                        SC_RESTORE,
-                        0);
-                    TRACE("Valid button clicked. App window Restored.\n");
-                }
-
-                SetForegroundWindow(TaskItem->hWnd);
-                TRACE("Valid button clicked. App window Activated.\n");
+                ::SwitchToThisWindow(TaskItem->hWnd, TRUE);
+                TRACE("Valid button clicked. App window Restored.\n");
             }
         }
     }