Add Weekly Roundup toggle to Notification settings

[renanferrari]

This PR adds an option in the Notification settings screen to disable Weekly Roundup notifications for a certain site.

This also adds an option on the Debug Settings screen to force show the Weekly Roundup notification, making it possible to test this without making any changes to the code.

To test

1. Login with an account that has at least one site that had more than 5 views in the past week.
2. On the Main screen, Tap the Me button.
3. On the Me screen, go to App Settings > Debug settings.
4. On the Debug Settings screen, scroll down to the Tools section and tap "Force show Weekly Roundup notification".
5. Wait for the Weekly Roundup notifications to show up (this might take a while).
6. Go back to the Main screen and tap the Notifications tab.
7. Tap the gear icon on the top right corner of the screen.
8. Under "Your sites", tap on one of the sites that had previously shown a Weekly Roundup notification.
9. Under "Notification Types", tap "App notifications".
10. Disable the Weekly Roundup option and tap "Ok".
11. Go back to the Debug settings screen and force show the Weekly Roundup notifications again.
12. Wait for the Weekly Roundup notifications to show up again.
13. Verify that the disabled site doesn't show a Weekly Roundup notification anymore.

Regression Notes

1. Potential unintended areas of impact
   Other notification settings.

2. What I did to test those areas of impact (or what existing automated tests I relied on)
   Manual testing and existing unit tests.

3. What automated tests I added (or what prevented me from doing so)
   Unit tests.

PR submission checklist:

• I have completed the Regression Notes.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[peril-wordpress-mobile]

You can trigger optional UI/connected tests for these changes by visiting CircleCI here.

[peril-wordpress-mobile]

	Warnings
⚠️	This PR is assigned to a milestone which is closing in less than 4 days Please, make sure to get it merged by then or assign it to a later expiring milestone

Generated by 🚫 dangerJS

[peril-wordpress-mobile]

You can test the changes on this Pull Request by downloading the APKs:

• Jetpack-pr-15325-build-115396.apk
• WordPress-pr-15325-build-115396.apk

[ravishanker]

LGTM 👍 Great job.