fix: fixing broken corners of table with sticky header bottom when scrolled

[dpitcock]

Fix for Sticky Header breaking bottom border at corners

The current implementation of the sticky header component can lead to a visual issue where the bottom corners of the sticky header jut out past the rounded borders of the table, causing a break in the visible border.

This pull request addresses this issue by making an enhancement to the useStickyHeader hook used by the Sticky Header and its parent component.

The key changes are:

Adding a new property called isStuckAtBottom to the object returned by the useStickyHeader hook. The isStuckAtBottom state is introduced to track whether the sticky header is aligned with the bottom edge of the table content. This is determined by comparing the bottom positions of the table container and the sticky header, and setting isStuckAtBottom accordingly. The internal table component then uses this state to apply an additional CSS class when the sticky header is in use, is stuck, and is stuck at the bottom edge, enabling the fix for the visual issue with the bottom border corners.

This fix should resolve the issue described in AWSUI-60364, providing a seamless visual experience for users when working with sticky headers in tables.

How has this been tested?

• unit tests added and updated
• integ tests uneffected
• visual regression tests have only one expected change with the corrected borders in dev-v3-denpitco pipeline

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.42%. Comparing base (f8f32c5) to head (a00ce27).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #3291    +/-   ##
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  Coverage   96.41%   96.42%            
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  Files         791      791            
  Lines       22564    22572     +8     
  Branches     7727     7383   -344     
========================================
+ Hits        21756    21764     +8     
- Misses        754      801    +47     
+ Partials       54        7    -47     

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