Run the functional tests faster and without the login timeout cascade

Problem/Motivation

The varbase-e2e CI jobs build and install a full site in each job, and create the testing users through the browser.

On a cold site, the first Webmaster login can time out (page.goto, 30 s). The users are then never made, and about 20 later scenarios fail together.

MR !43 failed this way and passed on a rerun. The Varbase job takes about 20 minutes.

Steps to reproduce

1. Watch the varbase-e2e-test job on a busy runner.
2. The first scenario, "Webmaster can log in and provision the rest of the testing users", times out.
3. The media library and settings scenarios after it fail.

Proposed resolution

Do what varbase_starter does:

• One build job per lane installs the site, applies the fixtures recipe, sets the robot settings, creates the users with drush, and dumps the database.
• The test jobs restore the dump, rebuild caches, warm the first pages with curl, and run in two shards.
• Cucumber gets retry: 1.
• The login scenario checks that each login lands on the user page.
• No scenario is dropped.

Remaining tasks

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

User interface changes

• N/A

API changes

• N/A

Data model changes

• N/A

Release notes snippet

• N/A

AI-Generated: Yes