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/Converters/StringToIntegerConverter.cs

@@ -0,0 +1,18 @@
+using System.ComponentModel;
+using System.Globalization;
+
+namespace Spectre.Console.Tests.Data
+{
+    public sealed class StringToIntegerConverter : TypeConverter
+    {
+        public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
+        {
+            if (value is string stringValue)
+            {
+                return int.Parse(stringValue, CultureInfo.InvariantCulture);
+            }
+
+            return base.ConvertFrom(context, culture, value);
+        }
+    }
+}