Overhaul Firefox feature pages [fix #11144]

[craigcook]

One-line summary

Updates Firefox feature pages. Some are rewrites of prior pages, some are brand new, some are reskins of existing pages, and some have been removed entirely.

The original plan was to preserve the old pages as fallbacks and only show the new ones for completed locales, at least for a while. But along the way that idea become untenable because so many are new or total rewrites, and several old pages were so outdated they weren't worth preserving. So this is a clean sweep and fresh start.

Significant changes and points to review

Lots of new strings and some string removal so that stuff needs some careful attention (I'll also ask Peiying for a review when she has time).

Issue / Bugzilla link

#11144

Testing

https://www-demo2.allizom.org/en-US/firefox/features/

http://localhost:8000/firefox/features/

[craigcook]

To do:

• Image for "Is Firefox a fast browser?"
• Image for "Is Firefox a private browser?"
• Image for the footer CTA (shown to non-Firefox)
• Add/update Pontoon configs
• Add/update tests

[craigcook]

Some test failures, marking do-not-merge until I can sort that out.

[craigcook]

The integration test failures seem unrelated and may just be a timeout on the test runner (it keeps failing on redirect tests, but not on any redirects I added/changed, and fails on different ones each time...). So removing the DNM tag and this is ready for review... but with caution. In a worst case, once it merges we'll see if tests pass on dev and if not, we can fix it there and/or revert the merge and dig deeper.

[craigcook]

Successful test run(!): https://github.com/mozilla/bedrock/actions/runs/5765257018

[reemhamz]

This was a wild PR. Good job on getting it through the door! 🎉

Main thing that is (potentially) blocking would be the updated strings in adblocker.ftl file. Check with Peiying if they're going to be deleting strings from their end before we implement this change. If not, then let's update the names of the FTL variables.

Some other notable comments I have are just surrounding visible a11y, where image borders would be nice to add for screenshots + changing body text to black to make it more readable.

[reemhamz]

This looks good to me. However, how come some of the new FTL files have -2023 in their name? I think those would be fine to remove?
r+w(possible)c 🎉

[craigcook]

This looks good to me. However, how come some of the new FTL files have -2023 in their name? I think those would be fine to remove?

The dated files are ones that already existed but were completely rewritten, so it seemed better to delete the old file and add a brand new one rather than replace every string in an existing file. Some others have been translated but just have a few new strings and we don't want to throw out those translations so I kept the filenames. And still others are brand new pages so maybe those Fluent files should also be dated, just to be consistent.

[reemhamz]

Currently in code-freeze for all-hands. Code freeze lifts August 28th.