Reimplemented StretchingOverscrollIndicator with Simulation ported from Android 12.

[MTtankkeo]

Fixed an issue #169659

This PR improves the StretchingOverscrollIndicator to better match native Android behavior.

• Previously, the stretch effect worked well only for slow dragging, and during fast flings it was absent or felt clipped.
• Implemented a Simulation-based animation that responds naturally to both slow drags and high-velocity flings.
• The result closely resembles the native Android overscroll behavior while maintaining Flutter's performance characteristics.

This change ensures that momentum-based gestures produce a more natural and intuitive overscroll experience, especially for users accustomed to native Android scroll views.

Fling

3.mp4

Pull And Reduce

Also, a very similar animation is implemented when pulling as well.

3.mp4

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].
• I followed the [breaking change policy] and added [Data Driven Fixes] where supported.
• All existing and new tests are passing.

[gemini-code-assist]

Code Review

This pull request is a great improvement to the StretchingOverscrollIndicator, replacing the previous animation logic with a more physically realistic SpringSimulation. This results in a much more natural feel, especially for high-velocity flings, aligning it better with native Android behavior. The code is well-structured, and the addition of a regression test is appreciated.

I've found a critical issue related to animation controller lifecycle management that could lead to race conditions. I've also identified a couple of medium-severity issues related to code clarity and maintainability. Addressing these will make the implementation more robust and easier to understand.

Overall, this is a high-quality contribution.

[dkwingsmt]

Thank you for this amazing change! My first round of review focuses on the constants for the spring simulation.

[dkwingsmt]

I'd let @Piinks double check one last time with everything. However @Piinks is out for the week and will return by Oct 20.

[Piinks]

Thanks Tong! I am rebasing here since it looks like there is no Google testing instance currently. We need that to validate we have resolved any remaining failures before merging.

[Piinks]

Checking in here: there are many failing tests behind the Google testing check here. I am working through them to validate the changes are expected, for example screenshot tests that captured the overscroll state.