Add usage scenarios to the Varbase functional testing suite and move to varbase-e2e 2.0.7

Problem/Motivation

The suite checks the content model, but not that an editor can publish an episode and a listener can find and play it.

Proposed resolution

• New scenarios: editor to reviewer publishing, mp3 upload through the media library, anonymous listener journey, drafts hidden from the listing, search and sitemap, SEO basics, accessibility on the listing and an episode page.
• Tighten the existing scenarios, add named selectors, tag every scenario, and purge what each scenario creates so the suite re-runs on the same site.
• Move to @vardot/varbase-e2e ^2.0.7 and its stricter accessibility gate.

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

Release notes snippet

• task: #3625560 Add usage scenarios to the Varbase functional testing suite and move to varbase-e2e 2.0.7.

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