[quick_actions_ios] UIScene Migration

[okorohelijah]

Migrate quick_actions_ios to adopt UIScene

Fixes #170179

Pre-Review Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter.
• I signed the CLA.
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I linked to at least one issue that this PR fixes in the description above.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or I have commented below to indicate which version change exemption this PR falls under¹.
• I updated CHANGELOG.md to add a description of the change, following repository CHANGELOG style, or I have commented below to indicate which CHANGELOG exemption this PR falls under¹.
• I updated/added any relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or I have commented below to indicate which test exemption this PR falls under¹.
• All existing and new tests are passing.

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Footnotes

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[gemini-code-assist]

Code Review

This pull request migrates the quick_actions_ios plugin to support the UIScene lifecycle, which is necessary for modern iOS apps. The changes involve conforming to FlutterSceneLifeCycleDelegate, implementing new lifecycle methods for scenes, and updating the example app to enable scene support. New tests for the scene-based lifecycle have also been added. My review focuses on ensuring the new lifecycle methods are implemented correctly and that the tests are robust.