Tests: Add new test assemblies for C# features (#36)

* Add new test assemblies for C# features

Three of these test assemblies go over several important features of C#,
organized by C# language version. PartialGenericTypes stresses closed
and partially closed generics. Finally, VTablesAndLayout tests the
layout of classes when translated to C++, and also contains code which
calls vtable and interface functions to test reverse engineering.

* Tests: Update .csproj

* Tests: Update .csproj

Co-authored-by: Katy Coe <djkaty@users.noreply.github.com>

Il2CppTests/TestSources/CSharp3.cs

@@ -0,0 +1,25 @@
+using System;
+using System.Linq;
+
+/* C# 3.0 feature test */
+namespace Il2CppTests.TestSources
+{
+    public class FeatureTest
+    {
+        public string AutoProp { get; set; }
+        public void AnonType() {
+            var c = new { Value = 3, Message = "Nobody" };
+            Console.WriteLine(c);
+        }
+
+        public int Linq() {
+            var scores = new int[] { 1, 2, 3, 4 };
+            var highScoresQuery =
+                from score in scores
+                where score > 80
+                orderby score descending
+                select score;
+            return highScoresQuery.Count();
+        }
+    }
+}