Added the option to close DB without saving

Changed the way recent files are retrieved
Stopped showing the DB Closed exception on suspend
Reordering entries works
Moved code from infra to application
Cleanup

ModernKeePass/Views/MainPageFrames/OpenDatabasePage.xaml.cs

@@ -42,7 +42,7 @@ namespace ModernKeePass.Views
             picker.FileTypeFilter.Add(".kdbx");
             
             // Application now has read/write access to the picked file
-            var file = await picker.PickSingleFileAsync();
+            var file = await picker.PickSingleFileAsync().AsTask();
             if (file == null) return;