chore(test): prepare tests to be run with Puppeteer-Firefox (#3833)

This patch aligns Puppeteer testing infrastructure with the approach
we use in Puppeteer-Firefox.

This patch:
- makes all tests accept Puppeteer object as a function argument
  rather than require it statically. This way we can pass either
  Puppeteer or Puppeteer-Firefox to drive tests.
- renames the `puppeteer.spec.js` into `launcher.spec.js`. The
  `puppeteer.spec.js` is now the entry point for all cross-browsers
  tests.

test/golden-chromium/jscoverage-involved.txt

@@ -0,0 +1,28 @@
+[
+  {
+    "url": "http://localhost:<PORT>/jscoverage/involved.html",
+    "ranges": [
+      {
+        "start": 0,
+        "end": 35
+      },
+      {
+        "start": 50,
+        "end": 100
+      },
+      {
+        "start": 107,
+        "end": 141
+      },
+      {
+        "start": 148,
+        "end": 160
+      },
+      {
+        "start": 168,
+        "end": 207
+      }
+    ],
+    "text": "\nfunction foo() {\n  if (1 > 2)\n    console.log(1);\n  if (1 < 2)\n    console.log(2);\n  let x = 1 > 2 ? 'foo' : 'bar';\n  let y = 1 < 2 ? 'foo' : 'bar';\n  let z = () => {};\n  let q = () => {};\n  q();\n}\n\nfoo();\n"
+  }
+]