fix: iOS PiP cleanup

[santhoshvai]

💡 Overview

• Guarenteed way to cleanup after view is unmounted
• reverts fix: stop picture-in-picture after call ends or goes to backstage #1854 as now there is a guarenteed and also that PR caused the cached property to hold a strong reference and so deinit was never called.

📝 Implementation notes

uses didMoveToSuperview instead of didMoveToWindow to ensure cleanup is always done on unmount

Here is Gemini 2.5 explanation of why to prefer didMoveToSuperView

Potential pitfalls for "unmounting" detection via didMoveToWindow in RN:

1. View removed from superview, but parent not in a window: If a view is removed from a superview, and that superview (or its ancestor) was never actually added to a window, didMoveToWindow might not have been called with a nil window because the view never had a non-nil window to begin with.

2. Container view removed: If you have a complex view hierarchy (e.g., ViewA contains ViewB, and ViewA is removed from its superview), ViewA and all its subviews (including ViewB) will have their superview become nil. However, didMoveToWindow might only be called on ViewA with nil, and ViewB would receive didMoveToSuperview with nil, but its didMoveToWindow might not fire again if it never had a window. (Though, typically, if a view is removed from a hierarchy that was in a window, its didMoveToWindow would also be called with nil).

3. App backgrounding/foregrounding: When your app goes to the background, views might be removed from the window. When it comes back to the foreground, they might be re-added. didMoveToWindow will be called in these scenarios, which might not be what you consider "unmounting" if you're specifically looking for removal from the view hierarchy rather than screen visibility changes.

[santhoshvai]

Released as below for testing

@stream-io/[email protected]

[santhoshvai]

mrged as it was tested externally and was confirmed to be working