Add new Subscribers tab

[aditi-bhatia]

Fixes https://github.com/wordpress-mobile/WordPress-Android/issues/20680

This PR adds in some basic groundwork for the new Subscribers tab, which is feature flagged behind stats_traffic_subscribers_tab. It is currently using mapInsights from UiModelMapper.kt as a placeholder for now, which is why you will see the screen below:

I've left the uses cases empty for now as that work can be done in a separate PR.

---

To Test:

1. With the stats_traffic_subscribers_tab feature flag on, ensure you see the Subscribers tab as it appears in the screenshot above.
2. Accessing the Subscribers tab should fire the stats_subscribers_accessed tracked event.
3. With the stats_traffic_subscribers_tab feature flag off, ensure you don't see the Subscribers tab and the weeks/days/months tabs appear as expected.

---

Regression Notes

1. Potential unintended areas of impact

   • States related to the stats_traffic_subscribers_tab feature flag

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

   • Manual testing

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

   • Tests will be updated in future PRs as development continues

---

PR Submission Checklist:

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

---

Testing Checklist (strike-out the not-applying and unnecessary ones):

• [ ] ~WordPress.com sites and self-hosted Jetpack sites.~
• [ ] ~Portrait and landscape orientations.~
• [ ] ~Light and dark modes.~
• [ ] ~Fonts: Larger, smaller and bold text.~
• [ ] ~High contrast.~
• [ ] ~Talkback.~
• [ ] ~Languages with large words or with letters/accents not frequently used in English.~
• [ ] ~Right-to-left languages. (Even if translation isn’t complete, formatting should still respect the right-to-left layout)~
• [ ] ~Large and small screen sizes. (Tablet and smaller phones)~
• [ ] ~Multi-tasking: Split screen and Pop-up view. (Android 10 or higher)~

[dangermattic]

	2 Warnings
:warning:	strings.xml files should only be updated on release branches, when the translations are downloaded by our automation.
:warning:	PR is not assigned to a milestone.

Generated by :no_entry_sign: Danger

[wpmobilebot]

📲 You can test the changes from this Pull Request in WordPress by scanning the QR code below to install the corresponding build.

	App Name	WordPress
	Flavor	Jalapeno
	Build Type	Debug
	Version	pr20685-2112f8f
	Commit	2112f8f75c13f9de90e4b54dfed22f7ffc92aec2
	Direct Download	wordpress-prototype-build-pr20685-2112f8f.apk

Note: Google Login is not supported on these builds.

[wpmobilebot]

📲 You can test the changes from this Pull Request in Jetpack by scanning the QR code below to install the corresponding build.

	App Name	Jetpack
	Flavor	Jalapeno
	Build Type	Debug
	Version	pr20685-2112f8f
	Commit	2112f8f75c13f9de90e4b54dfed22f7ffc92aec2
	Direct Download	jetpack-prototype-build-pr20685-2112f8f.apk

Note: Google Login is not supported on these builds.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 10.52632% with 17 lines in your changes are missing coverage. Please review.

Project coverage is 40.62%. Comparing base (ed25d7d) to head (2112f8f).

Files	Patch %	Lines
...droid/ui/stats/refresh/lists/StatsListViewModel.kt	6.66%	14 Missing :warning:
...rdpress/android/ui/stats/refresh/StatsViewModel.kt	0.00%	2 Missing :warning:
.../wordpress/android/ui/stats/refresh/StatsModule.kt	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## trunk #20685 +/- ## ========================================== - Coverage 40.63% 40.62% -0.01% ========================================== Files 1485 1485 Lines 68288 68307 +19 Branches 11296 11296 ========================================== + Hits 27746 27748 +2 - Misses 38029 38046 +17 Partials 2513 2513 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[sonarcloud[bot]]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud

[irfano]

I'm merging but I want to remind you that you can complete the "Regression Notes", "PR Submission Checklist" and "Testing Checklist" sections after the merge, @aditi-bhatia.

[aditi-bhatia]

Thank you for the reminder! I've gone ahead and updated those sections.