[inflight regression][iOS] Fix CarouselView2 dropping scrolls after ItemsSource swap/reset

[SyedAbdulAzeemSF4852]

Note

Are you waiting for the changes in this PR to be merged?
It would be very helpful if you could test the resulting artifacts from this PR and let us know in a comment if this change resolves your issue. Thank you!

Issue Details

• On iOS 18.5 and Mac (CI only), the CarouselViewShouldScrollToRightPosition and VerifyCarouselScrollsToEndItemAfterReset UI test are failing in candidate PR July 13th, Candidate #36411 due to the fix in PR [iOS/Mac][CV2] Fix CarouselView2 freezes with infinite loop when IsScrollAnimated=False #35848.

Root Cause

• PR [iOS/Mac][CV2] Fix CarouselView2 freezes with infinite loop when IsScrollAnimated=False #35848's _gotoPosition guard in CarouselViewController2 (iOS) is set by every call to ScrollToPosition and expected to be cleared by the scroll callback, but two internal scrolls — the SetValueFromRenderer(Position, 0) in UpdateItemsSource's reset branch and the forced ScrollToPosition(target, target, animated:false, forceScroll:true) at the end of CollectionViewUpdated — set it without producing a callback, so the stale value silently drops the next programmatic scroll.

Description of Change

• Cleared _gotoPosition when updating the items source to prevent scroll targets from the old source affecting the new data.
• Cleared _gotoPosition after resetting the Position property to ensure future programmatic changes are not suppressed.
• Cleared _gotoPosition during teardown to avoid leftover scroll targets when the view is re-attached.
• Cleared _gotoPosition after a forced scroll in CollectionViewUpdated to prevent suppression of later user-initiated scrolls.
• Cleared _gotoPosition after the forced scroll in UpdateLoop() to prevent it from becoming stale when the Loop property is toggled and the previous re-centering scroll is skipped or does not generate a callback.

Issues Fixed

Fixes #36718

Validated the behaviour in the following platforms

• Windows
• Android
• iOS
• Mac

Output

TestCase	Before	After
VerifyCarouselScrollsToEndItemAfterReset
CarouselViewShouldScrollToRightPosition

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[dotnet-policy-service]

Hey there @@SyedAbdulAzeemSF4852! Thank you so much for your PR! Someone from the team will get assigned to your PR shortly and we'll get it reviewed.

[sheiksyedm]

/azp run maui-pr-uitests , maui-pr-devicetests

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