test: migrate test.js to support concurrent test execution (#1531)

This patch migrates tests so that they can be run concurrently.

- By default, tests still run in one thread.
- To run tests in 4 parallel threads, run node test/test.js -j 4 or npm run unit -- -j 4
- Environment variable PPTR_PARALLEL_TESTS could be set to override default parallelization

Every test gets passed in a state. State is set up in the beforeAll and beforeEach callbacks,
and should be teared down in the afterAll and afterEach callbacks.

By default, state has a parallelIndex variable initialized that defines the thread index that runs the execution.

test/frame-utils.js

@@ -67,7 +67,7 @@ const utils = module.exports = {
    */
   dumpFrames: function(frame, indentation) {
     indentation = indentation || '';
-    let result = indentation + frame.url();
+    let result = indentation + frame.url().replace(/:\d{4}\//, ':<PORT>/');
     for (const child of frame.childFrames())
       result += '\n' + utils.dumpFrames(child, '    ' + indentation);
     return result;