Validation timing: saveWhileTyping supported for boolean

### Description

In the context of enhanced UX: it is desired to validate an intput field as soon as the user has left the field, before hitting a navigation button (triggers the validateOnNext-property). This was possible in frontend v. 3 through the 'saveWhileTyping'-property adjusting to boolean besides number.

Example: input field which stores a number. Immediate validation may feel aggressive, while validateOnNext unnecessarily delays the response time.

### Additional Information

_No response_

Start by tracing the saveWhileTyping and validateOnNext properties in the frontend code and their validation flow. Confirm the expected behavior for a boolean saveWhileTyping value, including validation when the user leaves an input before navigation, and add or update the relevant tests if they are found.

Written by the indexing model from the issue text.