Fix discarded quick start notification observers

[crazytonyli]

Relates to #20994.

All the notification handlers in this PR use weak self reference. That means, even though the observer and the handler block is not being released and called when those notification are emitted, the actually code may not get executed if self has already been released.

There are a few places where a stopObservingQuickStart function removes the wrong observer, which not only won't stop observing quick start, but also may incorrectly cause other notification handling code not get executed. However, I have checked all the stopObservingQuickStart call sites, all of them are called from a deinit function, so this removing wrong observers code probably doesn't actually cause any issue at the moment.

Regarding testing, I'm not sure how to test this change. Is Quick Start still an active feature? If so, how can I trigger it?

Regression Notes

1. Potential unintended areas of impact
   None.

2. What I did to test those areas of impact (or what existing automated tests I relied on)
   None.

3. What automated tests I added (or what prevented me from doing so)
   None.

PR submission checklist:

• I have completed the Regression Notes.
• I have considered adding unit tests for my changes.
• 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.

UI Changes testing checklist: N/A

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[staskus]

Thanks for the work!

I made a few comments, most of them are about the same thing, usage of #selector vs block observer. As I understand, we could use selector observers to avoid explicit removal of observer in deinit?

Regarding testing, I'm not sure how to test this change. Is Quick Start still an active feature? If so, how can I trigger it?

Yes, it is used. It can be triggered both with a new site and an existing site. You can check QuickStartFactory to see use cases.

1	2	3

✅ I tested and the quick start functionality continues to be working.

However, I noticed that:

• deinit is never called anywhere, even after logout. Memory debugger shows many VCs, Cells, Services continue to be initialized when only the login view is shown. Hard for me to imagine it's intentional, so I suspect more memory leaks are in play
• DashboardQuickActionsCardCell is always initialized and startObservingQuickStart is called regardless if quick start is actually shown or not. Again, I suspect some issues in the dashboard implementation

I'll investigate a bit more and create issues if necessary

[staskus]

Thank you for the changes! LGTM! ✅