[Tags Feed] Update feed tags as Diff, keeping existing tag content

[thomashorta]

Fixes #20811

When a new onTagsChanged is called and the current UI State is Loaded, let's just update the tags list and keep any content we already fetched before, by:

• Removing rows from tags that are not in the new call
• Adding rows for tags in the new call in the appropriate position, in the Initial state
• Using modifier to animate content to the correct place, using tag slug as key

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To Test:

1. Open Jetpack
2. Make sure reader_tags_feed Feature Config is ON
3. Go to Reader
4. Go to Your Tags feed
5. Scroll horizontally in one of the tags and tap More from
6. Unfollow the tag
7. Go back
8. Verify the tag is removed from the list but the existing tags don't reload

You can also test adding a new tag by:

1. Go to Your Tags feed
2. Scroll horizontally in one of the tags and tap More from
3. Tap one of the posts
4. Tap a tag from the post that you don't follow yet
5. Follow that tag
6. Hit back until you're back in the Your Tags feed
7. Verify the new tag appears in the appropriate position and existing tags kept their state

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Regression Notes

1. Potential unintended areas of impact

   • N/A

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

   • N/A

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

   • Added unit tests for new scenarios
   • Update unit tests for existing scenarios

---

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.

---

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)

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

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

See analysis details on SonarCloud

[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	pr20860-13d03b1
	Commit	13d03b1
	Direct Download	wordpress-prototype-build-pr20860-13d03b1.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	pr20860-13d03b1
	Commit	13d03b1
	Direct Download	jetpack-prototype-build-pr20860-13d03b1.apk

Note: Google Login is not supported on these builds.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 40.91%. Comparing base (5bbddf0) to head (13d03b1).

Additional details and impacted files

@@                 Coverage Diff                 @@
##           feature/tags-ia   #20860      +/-   ##
===================================================
+ Coverage            40.88%   40.91%   +0.03%     
===================================================
  Files                 1493     1493              
  Lines                68770    68794      +24     
  Branches             11350    11352       +2     
===================================================
+ Hits                 28117    28149      +32     
+ Misses               38098    38091       -7     
+ Partials              2555     2554       -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[daniloercoli]

Nice work! LGTM.