Provide a validation mode that reacts to significant user input

[effad]

As shown in https://mail.openjdk.org/pipermail/openjfx-dev/2023-March/039335.html applications may want to have a "validate on significant user input" mode.

While we cannot solve the problem of what constitutes "significant user input", we may want to provide an API to let the application specify a trigger to re-evaluate a specific check.