Added SDL_ClickTrayEntry()

Also removed the app delegate from the tray code on Cocoa and folded that into SDL3AppDelegate.

Fixes https://github.com/libsdl-org/SDL/issues/11906

src/dynapi/SDL_dynapi.sym

@@ -1231,6 +1231,7 @@ SDL3_0.0.0 {
     SDL_GetTrayMenuParentTray;
     SDL_GetThreadState;
     SDL_AudioStreamDevicePaused;
+    SDL_ClickTrayEntry;
     # extra symbols go here (don't modify this line)
   local: *;
 };