Make sure builds are reproducible by fixing all tooling versions

Today, slaves images pulled latest chrome version at image build time (see https://github.com/nuxeo/nuxeo-ansible-jenkins/blob/master/roles/slave_tools/tasks/google-chrome.yml#L7).

This is somehow good for functional testing since it allows to detect early breaking change in evergreen browsers. And by definition of evergreen, end-users are always supposed to use the latest version anyway. Although we know some organizations will lock auto-upgrade of evergreen browser and will only upgrade from time to time.

However, it makes the build non-reproducible which is not good and forces us to be hyper-reactive when new browser release introduces a breaking change (see NXP-25057).

Ideally, on job SLAVE label should provide a locked chrome version. And maybe EVERGREEN label will provide latest evergreen browser versions?

Note: double check if there are no current plans to integrate sauce lab for Web UI ftests in which case, EVERGREEN slave will become useless at least for this project.

Implementation Detail
We can rely on Docker image tags.