Extend Table's onSingleRowSelected Event type with previously selected record

[mdindoffer]

Summary

Please extend the API of the onSingleRowSelected Event so that the event payload includes both the new selection and the previously selected one.

Why

This would simplify the "revert" or "undo" scenarios where users may want to go back to their previously selected row in a table. A more specific example of this is when a user is reminded there are unsaved pending changes and selecting a different row would lose them for good. This can be worked around by client code in userspace, but should be a part of the standard toolkit.