[two_dimensional_scrollables] optimizes tableview janks with >250k rows

[wangfeihang]

Description:

This PR optimizes the scrolling jank issue of the TableView component when the number of rows exceeds 250,000.

Root Cause:

The _updateFirstAndLastVisibleCell method in RenderTableViewport uses linear for-loop traversal on _columnMetrics and _rowMetrics to locate the visible boundary cells: _firstNonPinnedRow, _lastNonPinnedRow, _firstNonPinnedColumn, and _lastNonPinnedColumn. When the number of rows/columns is extremely large (e.g., >250k rows), this linear traversal causes significant main-thread blocking and scrolling jank.

Solution:

Replace the linear for-loop with binary search algorithm to find the visible boundary cells (_firstNonPinnedRow, _lastNonPinnedRow, _firstNonPinnedColumn, _lastNonPinnedColumn). Binary search reduces the time complexity from O(n) to O(log n), effectively optimizing the scrolling jank issue under large data volumes.

Fixes: #138271

Video performance comparison

before:
https://github.com/user-attachments/assets/ca5b8821-4bdb-411f-bb2c-63998ac7c0d9

after:
https://github.com/user-attachments/assets/ebbf96d9-9e04-4ede-ae79-cd433885d3ab

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 under[^1].
• 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 under[^1].
• 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 under[^1].
• All existing and new tests are passing.

[gemini-code-assist]

Code Review

This pull request introduces a significant performance optimization for TableView when dealing with a large number of rows. The linear search for visible cells has been replaced with a more efficient binary search, which will reduce scrolling jank. The implementation of the binary search is sound and new tests have been added to ensure correctness. My feedback includes a few suggestions related to repository contribution guidelines for the CHANGELOG.md and pubspec.yaml files, as well as a minor refactoring opportunity in the new test to improve maintainability.

[Piinks]

We cannot append to releases that have already shipped. You'll need to create a new release and update the version in the pubspec as well.

[wangfeihang]

Hi Piinks, I've fixed the above issues in the new commit. Could you please review it again? Thanks so much for your review!