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/Data/Commands/GiraffeCommand.cs

@@ -0,0 +1,14 @@
+using System.ComponentModel;
+using Spectre.Console.Cli;
+
+namespace Spectre.Console.Tests.Data
+{
+    [Description("The giraffe command.")]
+    public sealed class GiraffeCommand : Command<GiraffeSettings>
+    {
+        public override int Execute(CommandContext context, GiraffeSettings settings)
+        {
+            return 0;
+        }
+    }
+}