[cupertino_ui] Use super parameters in more places

[srawlins]

This is work towards dart-lang/sdk#59226

The lint rule use_super_parameters has a bug such that it didn't previously report these cases. But they will be reported soon.

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Test exempt, as this code is covered by existing static and runtime checks.

[flutter-dashboard]

It looks like this pull request may not have tests. Please make sure to add tests or get an explicit test exemption before merging.

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[gemini-code-assist]

Code Review

This pull request updates the constructors of the _Segment and _SegmentSeparator classes in sliding_segmented_control.dart to use super-initializer parameters for the key property. There are no review comments, and I have no feedback to provide.

[Piinks]

Thanks @srawlins! I think these will be safe to land in flutter/flutter as well so that dart-lang/sdk#47839 is not blocked from landing there. :)
Let me know if I can help with that.

For the PRs in cupertino_ui and material_ui, they will need a pending changelog file. See https://github.com/flutter/packages/pull/12381/files for an example. We have a new batch release process that pulls them all together into one changelog entry before a release.
There is a template in pending_changelogs/