[iOS] Fix for the CollectionView to prevent duplicate groups or crashes when adding a new item to a group or when adding a new group.

[Tamilarasan-Paranthaman]

Root Cause:

1. Add item in the group:

• Dequeuing a supplementary view for measurement caused multiple instances of the header and footer to appear in the view.

2. Adding new group:

• We checked if _collectionView.NumberOfSections() == 0 to determine whether a reload was required, in conjunction with the NotLoadedYet() condition.
• However, using _collectionView.NumberOfSections() caused a crash when the collection view was empty and a new group was added, as NumberOfSections() == 0 is always true for an empty collection. This check prevented the adding a new group.

Description of Change:

1. Add item in the group:

• We removed the version check and dequeuing logic to prevent the issue of duplicate header/footer templates.
• Now, we always use MeasureSupplementaryView, which calculates the size without dequeuing the view, ensuring that the supplementary is only rendered when necessary.

2. Adding new group:

• Modified the condition to check only if the collection view has not yet been loaded using the NotLoadedYet() method.
• By removing the section check and focusing solely on whether the collection view has been loaded, we ensure that the data reloads properly in both empty and populated states.

Validated the behaviour in the following platforms,

• Android
• Windows
• iOS
• Mac

Issues Fixed

Fixes #17969
Fixes #20336

Screenshots

After Issue Fix

Screen.Recording.mov

[dotnet-policy-service]

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

[PureWeen]

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[rmarinho]

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