Add an overload for ClassicDesktopStyleApplicationLifetime (#16167)

* add an overload with no parameters for ClassicDesktopStyleApplicationLifetime

* add an overload with no parameters for ClassicDesktopStyleApplicationLifetime

* add a new internal func: Startcore(args)

---------

Co-authored-by: Max Katz <maxkatz6@outlook.com>

src/Avalonia.Controls/ApplicationLifetimes/ClassicDesktopStyleApplicationLifetime.cs

@@ -117,16 +117,30 @@ namespace Avalonia.Controls.ApplicationLifetimes
         }
 
         public int Start(string[] args)
+        {
+            return StartCore(args);
+        }
+
+        /// <summary>
+        /// Since the lifetime must be set up/prepared with 'args' before executing Start(), an overload with no parameters seems more suitable for integrating with some lifetime manager providers, such as MS HostApplicationBuilder.
+        /// </summary>
+        /// <returns>exit code</returns>
+        public int Start()
+        {
+            return StartCore(Args ?? Array.Empty<string>());
+        }
+
+        internal int StartCore(string[] args)
         {
             SetupCore(args);
-            
+
             _cts = new CancellationTokenSource();
 
             // Note due to a bug in the JIT we wrap this in a method, otherwise MainWindow
             // gets stuffed into a local var and can not be GCed until after the program stops.
             // this method never exits until program end.
-            ShowMainWindow(); 
-                              
+            ShowMainWindow();
+
             Dispatcher.UIThread.MainLoop(_cts.Token);
             Environment.ExitCode = _exitCode;
             return _exitCode;