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/NoDescriptionCommand.cs

@@ -0,0 +1,16 @@
+using System.Diagnostics.CodeAnalysis;
+using Spectre.Console.Cli;
+
+namespace Spectre.Console.Tests.Data
+{
+    public sealed class NoDescriptionCommand : Command<EmptyCommandSettings>
+    {
+        [CommandOption("-f|--foo <VALUE>")]
+        public int Foo { get; set; }
+
+        public override int Execute([NotNull] CommandContext context, [NotNull] EmptyCommandSettings settings)
+        {
+            return 0;
+        }
+    }
+}