chore: stop using console.assert everywhere (#2646)

Since Node 10, `console.assert` no longer throws an AssertionError.
(This is generally good since it aligns Node.js with Browsers.)

This patch migrates all usages of `console.assert` in our codebase.
- All the `lib/` and testing code is migrated onto a handmade `assert`
function. This is to make Puppeteer transpilation / bundling easier.
- All the tooling is switched to use Node's `assert` module.

Fixes #2547.

utils/testrunner/Matchers.js

@@ -44,7 +44,8 @@ class Expect {
     function applyMatcher(matcherName, matcher, inverse, value, ...args) {
       const result = matcher.call(null, value, ...args);
       const message = `expect.${inverse ? 'not.' : ''}${matcherName} failed` + (result.message ? `: ${result.message}` : '');
-      console.assert(result.pass !== inverse, message);
+      if (result.pass === inverse)
+        throw new Error(message);
     }
   }
 }

utils/testrunner/TestRunner.js

@@ -316,7 +316,7 @@ class TestRunner extends EventEmitter {
   }
 
   _addHook(hookName, callback) {
-    console.assert(this._currentSuite[hookName] === null, `Only one ${hookName} hook available per suite`);
+    assert(this._currentSuite[hookName] === null, `Only one ${hookName} hook available per suite`);
     const hook = new UserCallback(callback, this._timeout);
     this._currentSuite[hookName] = hook;
   }
@@ -389,6 +389,15 @@ class TestRunner extends EventEmitter {
   }
 }
 
+/**
+ * @param {*} value
+ * @param {string=} message
+ */
+function assert(value, message) {
+  if (!value)
+    throw new Error(message);
+}
+
 TestRunner.Events = {
   Started: 'started',
   TestStarted: 'teststarted',