Tests: Add convenience function to pause execution without timing out

`await pause(this)` can be used to disable the test timeout and pause
execution so the UI state can be manually inspected

test/content/support.js

@@ -374,6 +374,14 @@ function waitForNotifierEvent(event, type) {
 	return deferred.promise;
 }
 
+/**
+ * Hang tests for manual inspection
+ */
+async function pause(thisObj) {
+	thisObj.timeout(100000000);
+	await Zotero.Promise.delay(100000000);
+}
+
 /**
  * Looks for windows with a specific URL.
  */