For #18262 - [Credit cards] Turn the "Sync cards across devices" button into a "Sync cards" toggle

[codrut-topliceanu]

For #18262

Pull Request checklist

• Tests: This PR includes thorough tests.
• Screenshots: This PR includes video of the changes made.
• Accessibility: The code in this PR follows accessibility best practices.

To download an APK when reviewing a PR:

1. click on Show All Checks,
2. click Details next to "Taskcluster (pull_request)" after it appears and then finishes with a green checkmark,
3. click on the "Fenix - assemble" task, then click "Run Artifacts".
4. the APK links should be on the left side of the screen, named for each CPU architecture

toggle.credit.cards.logins.sync.mp4

[mergify]

This pull request has conflicts when rebasing. Could you fix it @codrut-topliceanu? 🙏

[codecov-commenter]

Codecov Report

Merging #19207 (ce6c60f) into master (4ee8f15) will increase coverage by 0.00%.
The diff coverage is 45.71%.

@@            Coverage Diff            @@
##             master   #19207   +/-   ##
=========================================
  Coverage     34.62%   34.62%           
+ Complexity     1614     1613    -1     
=========================================
  Files           540      541    +1     
  Lines         21819    21828    +9     
  Branches       3251     3253    +2     
=========================================
+ Hits           7554     7558    +4     
- Misses        13367    13370    +3     
- Partials        898      900    +2     

Impacted Files	Coverage Δ	Complexity Δ
...settings/creditcards/CreditCardsSettingFragment.kt	23.72% <0.00%> (+0.39%)	7.00 <0.00> (ø)
...ettings/logins/fragment/SavedLoginsAuthFragment.kt	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
.../java/org/mozilla/fenix/settings/SyncPreference.kt	40.00% <40.00%> (ø)	1.00 <1.00> (?)
...a/org/mozilla/fenix/settings/SyncPreferenceView.kt	77.77% <85.71%> (-2.23%)	7.00 <0.00> (-2.00)

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[codrut-topliceanu]

Thank you for the help @gabrielluong 🥇

[gabrielluong]

I think we are super close! I am also super sorry for all these excessive comments that I am leaving in the review. I hope they were generally helpful.

I left some questions just to ask for clarifications.

[codrut-topliceanu]

I think we are super close! I am also super sorry for all these excessive comments that I am leaving in the review. I hope they were generally helpful.

I left some questions just to ask for clarifications.

Don't worry about it! This process increases the overall code quality ❤️

Btw: I'm clicking on "Resolve conversation" once I've addressed/reviewed/answered a comment, as a way to minimize it. That helps me a lot to not get lost in all of them. Feel free to un-resolve them when you add something further on them.

[gabrielluong]

Sorry, didn't get to this today, will review it tomorrow!

[gabrielluong]

Let's address the remaining new comments and land this. Please also flag for QA-needede and alert them about testing on both logins and credit cards. Can you also file an issue about that "Reconnect" conversation in #19207 (comment) and flag it for UX-investigation?

Thanks!