fix: do not fire change for time-picker value set programmatically (#12470) (CP: 25.2)

[vaadin-bot]

This PR cherry-picks changes from the original PR #12470 to branch 25.2.

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Original PR description

Description

Extracted from #12467

Depends on #12468

A value finer than the step allows, e.g. 10:00:30 with the default step, was marked as committed before being stripped to 10:00, so the next commit attempt fired change for a value the user never entered.

• Stripped the value to the step resolution before marking it as committed in _valueChanged, reusing the __getTimeObject() helper added in refactor: rewrite time-picker value formatting logic to use updated #12468
• Added test for committing a value set programmatically with milliseconds that the step strips

Type of change

• Bugfix

How to test

1. Open dev/time-picker.html
2. In the browser console, run:

   const timePicker = document.querySelector('vaadin-time-picker');
   timePicker.addEventListener('change', () => console.log('change'));
   timePicker.value = '10:00:30';

3. The field shows 10:00
4. Click the field, then click outside it
5. Nothing is logged

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud