Problems with UI form validation

Noticed the following issues

1. On a number component with +/- buttons, the UI sometimes doesn't show validation error. For example: packet-interval option in latency test which is optional and can have a value > 0, sometimes it will error out when i set packet interval to 0 and sometimes it doesn't

=> Fixed it by dispatching a change event when the +/- buttons are pressed

2. Another thing was that let's say i fill in a value. then i decide i don't want to fill in anything. it still errors out because it expects a value. For example, same packet-interval value in latency test expects a value between 0 and 1. But since it's not mandatory, i don't want to fill it in. However, the form doesn't let me submit it

=> Fixed this in ps-input-text.js, in the number case — treat an empty input as undefined (removing the key from form data) rather than converting to 0

3. Same issue with text fields. Filling an optional text field with an invalid value (e.g. a non-ISO 8601 string in connection-expires) shows a validation error. Clearing the field sets the value to "", which still fails the pattern validator — so the error persists and the form won't submit.

=> Fixed this by changing the default case in ps-input-text.js. Clearing any text field now sets `this.value = undefined` instead of `""`, which removes the key from form data entirely, so the pattern validator is never triggered for an absent optional field