Add W3C compliant JS testing

Migrated issue

Reported by: alexpott

Related to !248 (merged)

Problem/Motivation

Once #3421202: Enable W3C-compliant webdriver testing lands we will be able to run tests using selenium and the latest Chrome. We should support that in the template as eventually non-W3C testing will be deprecated.

Proposed resolution

• Update .testing-job-base to use the new Selenium driver and set the variables for the latest Chrome browser
• These will be the default for all test jobs, but temporarily revert to the legacy values for variants using Drupal 10 and lower
• This means that only "Nightwatch Next Major" and "PHPUnit Next Major" will use the new driver at the moment
• When Drupal 11 becomes 'current' then all jobs will use the new driver except 'Nightwatch Previous Major' and 'PHPUnit Previous Major'

User interface changes

If a contrib project does not want to test against W3C-compliant driver, the values can be reverted. Instructions for this are in the Nightwatch and PHPUnit documentation pages

Related issue: Issue #3421202

Related issue: Issue #3471104

Related issue: Issue #3469490