refactor: deprecate usage of Date in favor of Instant

[bwajtr]

Description

In relation to the Gantt chart support implementation, this change adds convenient methods setMin(Instant) and setMax(Instant) to the Axis class.

At the same time, the Date variants of these methods are marked as deprecated because the underlying Util.toHighchartsTS(Date) method that is being used by setMin and setMax is deprecated as well (from before).

Part of #4731

Type of change

• Bugfix
• Feature

Checklist

• I have read the contribution guide: https://vaadin.com/docs/latest/contributing/overview
• I have added a description following the guideline.
• The issue is created in the corresponding repository and I have referenced it.
• I have added tests to ensure my change is effective and works as intended.
• New and existing tests are passing locally with my change.
• I have performed self-review and corrected misspellings.
• I have not completed some of the steps above and my pull request can be closed immediately.

Additional for Feature type of change

• Enhancement / new feature was discussed in a corresponding GitHub issue and Acceptance Criteria were created.

[sonarqubecloud]

Quality Gate passed

Issues
2 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