Adding a rule that turns off assembly info generation for attributes already defined when migrating.

TestAssets/TestProjects/AppWithAssemblyInfo/Program.cs

@@ -0,0 +1,14 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace ConsoleApp1
+{
+    public class Program
+    {
+        public static void Main(string[] args)
+        {
+        }
+    }
+}