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/ThrowingCommand.cs

@@ -0,0 +1,17 @@
+using System;
+using Spectre.Console.Cli;
+
+namespace Spectre.Console.Tests.Data
+{
+    public sealed class ThrowingCommand : Command<ThrowingCommandSettings>
+    {
+        public override int Execute(CommandContext context, ThrowingCommandSettings settings)
+        {
+            throw new InvalidOperationException("W00t?");
+        }
+    }
+
+    public sealed class ThrowingCommandSettings : CommandSettings
+    {
+    }
+}