Enable parallel test execution, mark timing-sensitive test as non-parallel, and use Interlocked for TaskId

YesNt.Interpreter.Tests/AssemblyInfo.cs

@@ -0,0 +1,3 @@
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+[assembly: Parallelize(Workers = 0, Scope = ExecutionScope.MethodLevel)]

YesNt.Interpreter.Tests/ConsoleStatementsTests.cs

@@ -76,6 +76,7 @@ public class ConsoleStatementsTests
     }
 
     [TestMethod]
+    [DoNotParallelize] // timing-sensitive: relies on Thread.Sleep to let the interpreter reach %read_key
     public void ReadKeyCanBeInterruptedByStopTest()
     {
         YesNtInterpreter interpreter = new YesNtInterpreter();