task: #3622098 Test only with Drupal CMS and rename the test jobs to functional

Fixes #3622098.

Problem

Varbase Starter is a Drupal CMS site template, so Drupal CMS is the base it has to work on. The pipeline built two hosts — drupal/varbase_project and drupal/cms — which doubled the build time and split the coverage.

What changed

• Removed the varbase_project pre-test job and the VARBASE_PROJECT variable.
• Promoted the Drupal CMS job to the single pre-test job: it applies the i18n / api / auth / ai base recipes the suites exercise, seeds the testing users and dumps the DB for the test matrix.
• SITE_DIR / WEB_ROOT and the build cache point at cmssite/ instead of testsite/.
• Test jobs renamed to 🧪 functional and 🧪 functional (smoke). The test stage name is unchanged.

.gitlab-ci.yml only: 97 insertions, 209 deletions.

Known: this lane fails at install today

drupal/canvas resolves to 1.11.0, which fatals during install with You have requested a synthetic service ("kernel"). Upstream defect, not this change — stock drupal_cms_starter fails identically — tracked at drupal_cms#3591450 (closed). Canvas 1.10.1 installs clean, and Canvas is deliberately left unconstrained here.

So "Testing to ensure no regression" is not ticked: the new lane has not yet run green end to end.

AI-Generated: Yes

Checkpoints:

• File an issue
• Addition/Change/Update/Fix
• Testing to ensure no regression
• Automated unit testing coverage
• Automated functional testing coverage
• UX/UI designer responsibilities
• Readability
• Accessibility
• Performance
• Security
• Developer Documentation
• User Guide Documentation
• Reviewed by human
• Code review by maintainers
• Full testing and approval
• Credit contributors
• Review with the product owner
• Release notes snippet
• Release