[YiR] V2 - Saved Articles slide

[mazevedofs]

Phabricator: https://phabricator.wikimedia.org/T376067

Notes

• Adds the saved count slide for eligible users (logged-in users with more than 3 saved articles)
• Shows collective slide for the rest of users
• Saved count and the random saved article titles are retrieved from the main app core data and passed through an async call, using a delegate
• These new core data methods live in MWKSavedPageList
• Copy and assets are still outdated, no V2 updates were made

Test Steps

1. Logged in, device set to Italy or Mexico, set main language to en, es or it
2. Browse 7+ articles
3. Background the app
4. You should see the personalized saved article slide if you have more than 3 saved articles, plus the names of 3 random articles you saved
5. Remove saved article, leave 2 or less
6. Trigger the regeneration of the report (you can disable and re-enable the YiR repot in settings)
7. You should now see the collective slide
8. Logged out, in a device with any number of saved slides - you should always see the collective slide

[mazevedofs]

Opening as a draft so I can get feedback on some issues I'm having

[tonisevener]

Just some little things from code review. I will push these PR feedback tweaks.