fix: use unique cookie values for instant navigation testing lock
Newer Chromium versions (>=136, shipped with Playwright >=1.58) skip
CookieStore change events when a cookie is set to the same value it
already has. This broke nesting detection in the instant navigation
testing API because both the outer and inner instant() calls set the
cookie to '1'.
- Use a counter-based value in @next/playwright so each addCookies
call triggers a CookieStore change event
- Use Date.now() in the dev overlay panel for the same reason
- Increase retry timeouts in devtools test to accommodate slightly
slower badge status transitions in newer Chromium
- Update cookie value assertion to match dynamic values