LS26001825: kup-data-table editable: fix show error message ongli on "data" change

[pasere-smeup]

This pull request enhances error handling and user feedback in the kup-data-table component, particularly for errors present in hidden columns. The main changes include introducing a new callback prop for custom error message display, refactoring error detection logic, and updating documentation.

Error handling improvements:

• Added a new showMessage callback prop to the kup-data-table component, allowing consumers to provide a custom function for displaying error messages (such as errors in hidden columns), and updated the documentation to describe this prop (readme.md).
• Refactored the logic for detecting errors in hidden columns: extracted this check into a new checkHiddenColumnErrors method, which is triggered when the data property changes. If errors are found in hidden columns, the showMessage callback is invoked (kup-data-table.tsx).

Code simplification:

• Removed the previous logic that handled hidden column errors within the cell focus loop, delegating this responsibility to the new watcher method for better separation of concerns and code clarity (kup-data-table.tsx).