Add ts to globalThis for convenience during debugging

Author: jakebailey

Diff for: src/testRunner/runner.ts

@@ -280,6 +280,9 @@ function beginTests() {
 
 export let isWorker: boolean;
 function startTestEnvironment() {
+    // For debugging convenience.
+    (globalThis as any).ts = require("./_namespaces/ts");
+
     isWorker = handleTestConfig();
     if (isWorker) {
         return Parallel.Worker.start();