feat: Update Gitlab CI to run Cubicweb's tests with latest RQL's updates

Add a job that will:
- clone the last Cubicweb version
- update rql requirement within Cubicweb's setup.py
- finally, run tox -e py3-server

See #8
7 jobs for !62 with topic/default/test-cubicweb-with-last-rql-updates in 15 minutes and 23 seconds (queued for 6 seconds)
latest detached
Status Name Job ID Coverage
  Lint
passed check-manifest #460534

00:00:30

passed flake8 #460532

00:00:35

passed mypy #460533

00:00:34

passed yamllint #460535

00:00:32

 
  Tests
passed cubicweb-tests #460538

00:14:40

passed py3 #460536

00:00:38

passed py3-from-forge #460537

00:00:48