Enable running unit tests in parallel

not that it has a noticeable effect, I'm really just leaving this here so I don't forget later

src/BizHawk.Tests/EmbeddedData.cs

@@ -2,6 +2,10 @@ using System;
 using System.IO;
 using System.Reflection;
 
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+[assembly: Parallelize(Scope = ExecutionScope.MethodLevel)]
+
 namespace BizHawk.Tests
 {
 	public static class EmbeddedData