[cupertino_ui] Fix platform view sheet transitions

[laishere]

From flutter/flutter#182935
Fixes flutter/flutter#169495

The scale transition in showCupertinoSheet for the underlying route defaulted to FilterQuality.medium, which pushes an implicit ImageFilterLayer.

Platform views cannot be correctly sampled or transformed by rasterization-based filters. Consequently, they fail to reflect the scale transformation during the transition animation when an ImageFilterLayer is present, leading to a broken visual effect where the background scales but the platform view remains at its original size.

Solution:
Added hasPlatformView parameter. false by default which matches the original behavior. When set to true, we use standard TransformLayer by setting filterQuality to null.

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[gemini-code-assist]

Code Review

This pull request introduces a hasPlatformViews parameter to Cupertino sheet transitions, routes, and helper functions to ensure platform views remain synchronized during transitions by disabling image-filtered scaling. It also includes corresponding unit tests and a changelog entry. A review comment suggests using scrollableBuilder instead of the deprecated pageBuilder in the new tests.

[dkwingsmt]

LGTM. Thank you!

[laishere]

Here's the subpixel issue I mentioned about when using TransformLayer.
We can see the underlying route title will drift in the navigation bar when being scaled, while the default one uses ImageFilterLayer which has better rasterization result.

Raster.Drift.Comparison.When.Scaling.mp4

[laishere]

@dkwingsmt It shows one workflow awaiting approval. Is it required?