Moved analyzer tests to its own project

Also moves tests to `./test` which makes it possible
for all test projects to share the same .editorconfig
files and similar.

test/Spectre.Console.Tests/Utilities/Extensions/ShouldlyExtensions.cs

@@ -0,0 +1,20 @@
+using System;
+using System.Diagnostics;
+
+namespace Spectre.Console
+{
+    public static class ShouldlyExtensions
+    {
+        [DebuggerStepThrough]
+        public static T And<T>(this T item, Action<T> action)
+        {
+            if (action == null)
+            {
+                throw new ArgumentNullException(nameof(action));
+            }
+
+            action(item);
+            return item;
+        }
+    }
+}