chore(firefox): mark all Puppeteer tests that are failing on FF (#3924)

This patch:
- introduces new testRunner methods `addTestDSL` and `addSuiteDSL`
  to add annotated test / suite.
- introduces new test/suite declaration methods: `it_fails_ffox` and
  `describe_fails_ffox`. These are equal to `it`/`describe` for chromium
  tests and to `xit`/`xdescribe` for firefox.
- marks all unsupported tests with `it_fails_ffox`
- adds a new command-line flag `'--firefox-status'` to `//test/test.js`.
  This flag dumps current amount of tests that are intentionally skipped
  for Firefox.

End goal: get rid of all `it_fails_ffox` and `describe_fails_ffox`
tests.

Drive-By: remove cookie tests  "afterEach" hook that was removing
cookies - it's not needed any more since every test is run in a
designated browser context.

References #3889

test/cookies.spec.js

@@ -15,16 +15,11 @@
  */
 
 module.exports.addTests = function({testRunner, expect}) {
-  const {describe, xdescribe, fdescribe} = testRunner;
+  const {describe, xdescribe, fdescribe, describe_fails_ffox} = testRunner;
   const {it, fit, xit} = testRunner;
   const {beforeAll, beforeEach, afterAll, afterEach} = testRunner;
 
-  describe('Cookies', function() {
-    afterEach(async({page, server}) => {
-      const cookies = await page.cookies(server.PREFIX + '/grid.html', server.CROSS_PROCESS_PREFIX);
-      for (const cookie of cookies)
-        await page.deleteCookie(cookie);
-    });
+  describe_fails_ffox('Cookies', function() {
     it('should set and get cookies', async({page, server}) => {
       await page.goto(server.PREFIX + '/grid.html');
       expect(await page.cookies()).toEqual([]);