WNP 137

[alexgibson]

One-line summary

Replaces #16103

Significant changes and points to review

New UITour capability: https://firefox-source-docs.mozilla.org/browser/components/uitour/docs/UITour-lib.html#Mozilla.UITour.openPreferences

• should be able to open directly at "Browser Layout" section

This is developed with the expectation of Firefox 137 being the browser it's viewed in. Let me know if we want to be a little more defensive in case it's viewed outside of that browser.

Issue / Bugzilla link

#16086
#16109

Testing

Video loads on click only
Check window.dataLayer for video play and pause events

Vertical tabs
http://localhost:8000/en-US/firefox/137.0/whatsnew/
http://localhost:8000/en-CA/firefox/137.0/whatsnew/
http://localhost:8000/en-GB/firefox/137.0/whatsnew/
http://localhost:8000/fr/firefox/137.0/whatsnew/
http://localhost:8000/de/firefox/137.0/whatsnew/

default: http://localhost:8000/es/firefox/137.0/whatsnew/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.56%. Comparing base (0f51540) to head (cfeb047).
Report is 17 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16125      +/-   ##
==========================================
+ Coverage   79.52%   79.56%   +0.04%     
==========================================
  Files         160      160              
  Lines        8438     8440       +2     
==========================================
+ Hits         6710     6715       +5     
+ Misses       1728     1725       -3     

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[alexgibson]

This PR has been previously reviewed in #16103, bar a couple of tiny changes. Merging this rather than starting another round of review.