Add drupalci.yml test file to configure d.o. testing

This contains a bit of guess-work.

Use $PROJECT_DIR not $SOURCE_DIR this time.

The default drupalci config (and the default behaviour before I added drupalci.yml) attempts to run every type of test. In particular we have:

    testing:
      run_tests.standard:
        types: 'Simpletest,PHPUnit-Unit,PHPUnit-Kernel,PHPUnit-Functional'
        run_tests.js:
        concurrency: 1
        types: 'PHPUnit-FunctionalJavascript'
      nightwatchjs:

Then we get console error messages such as:

php /var/www/html/core/scripts/run-tests.sh --color --keep-results --suppress-deprecations --types "PHPUnit-FunctionalJavascript" --concurrency "1" --repeat "1" --sqlite "/var/lib/drupalci/workdir/run_tests.js/simpletest.sqlite" --dburl "mysql://drupaltestbot:drupaltestbotpw@172.18.0.4/jenkins_drupal_contrib_339955" --url "http://php-apache-jenkins-drupal-contrib-339955/subdirectory" --directory modules/contrib/scheduler
> Drupal\Core\Composer\Composer::upgradePHPUnit
   ERROR: No valid tests were specified.

and

$ cross-env BABEL_ENV=development node -r dotenv-safe/config -r babel-register ./node_modules/.bin/nightwatch --config ./tests/Drupal/Nightwatch/nightwatch.conf.js --tag=scheduler
 There was an error while starting the test runner:

As we do not have javascript tests it is cleaner to remove these attempts from drupalci.yml

Yes! Now we do not get the errors in Jenkins console saying 'No valid tests were specified'

Calling this fixed now. There are lots of other things we can do with drupalci.yml and they can be on other issues.

For the record, to temporarily limit the Scheduler phpunit tests on D.O. to a single test class, the following line can be added:

testgroups: '--class "Drupal\Tests\scheduler\Functional\NameOfTest"'

where NameOfTest is the test class. Note that the full path is case-sensitive.

Setting to active to allow tests to be run.

Ignore the above patches. Using this issue for D9 drupalci.yml patch testing.