[material_ui] Port PR (#188729) from flutter/flutter to material_ui

[puneetkukreja98]

This PR ports flutter/flutter#188729 from flutter/flutter to flutter/packages

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[gemini-code-assist]

Code Review

This pull request adds a sortIconBuilder parameter to DataTable, PaginatedDataTable, and DataTableThemeData to support custom sorting indicators, along with corresponding tests and documentation. Feedback suggests simplifying the theme resolution in DataTable by removing the redundant fallback to themeData.dataTableTheme.sortIconBuilder, as DataTableTheme.of(context) already handles this fallback.

[gemini-code-assist]

The fallback to themeData.dataTableTheme.sortIconBuilder is redundant and inconsistent with Flutter's theme resolution pattern.

DataTableTheme.of(context) already returns Theme.of(context).dataTableTheme if there is no inherited DataTableTheme ancestor. In Flutter, if an inherited theme is present, it completely overrides the global theme rather than merging with it. Therefore, we should only resolve from sortIconBuilder and dataTableTheme.sortIconBuilder.

    final DataTableSortIconBuilder? effectiveSortIconBuilder =
        sortIconBuilder ?? dataTableTheme.sortIconBuilder;

[Piinks]

Oh yeah. This is correct.