Fix memory leak in CupertinoActionSheet

[ksokolovskyi]

This PR fixes memory leaks in the CupertinoActionSheet widget, which did not dispose ScrollControllers created internally.

Description

• Converts CupertinoActionSheet from StatelessWidget to StatefullWidget;
• Fixes ScrollController not disposed in tests #134862.

Tests

• Updates cupertino/action_sheet_test.dart to use testWidgetsWithLeakTracking.

Pre-launch Checklist

• I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
• I read the [Tree Hygiene] wiki page, which explains my responsibilities.
• I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement].
• I signed the [CLA].
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is [test-exempt].
• All existing and new tests are passing.

[ksokolovskyi]

cc @polina-c

[polina-c]

I think we duplicated each other: #13479
And the changes are almost identical.

I will merge yours, because in this case I do not need approver from Flutter team.

[ksokolovskyi]

I think we duplicated each other: #13479 And the changes are almost identical.

I will merge yours, because in this case I do not need approver from Flutter team.

Thanks a lot for the review, and sorry for the duplication of your fix. Next time, I will be more attentive.