Make VMs start in full screen

I figured I'd try this to see if it makes VMs start up in full screen.
(I tested it a little bit, and it seems to work.)

This is my initial attempt to look at issue utmapp#4304. However, it definitely
doesn't fix that issue (yet), because it goes from VMs *never* starting
in full screen to *always* starting in full screen.

(I do intend to try a similar patch against the main branch, and
possibly try to develop a proper patch after that. However, my
current build environment has many problems, so I need to recreate
my build environment from scratch before I continue.)

Platform/macOS/UTMDataExtension.swift

@@ -48,6 +48,7 @@ extension UTMData {
             vmWindows[vm] = unwrappedWindow
             unwrappedWindow.showWindow(nil)
             unwrappedWindow.window!.makeMain()
+            unwrappedWindow.window!.toggleFullScreen(nil)
             unwrappedWindow.requestAutoStart()
         } else {
             logger.critical("Failed to create window controller.")