fix(datetimepickerv2): add onClear callback

[jessieyan]

Closes #3760

Summary

• Before we don't have onClear call back for user to reset date and time values.

Change List (commits, features, bugs, etc)

• added onClear() callback prop for single select

Acceptance Test (how to verify the PR)

• Go to single select story
• Click on calendar button
• Click on clear button
• In action tab, see onClear was being called with empty objects

Regression Test (how to make sure this PR doesn't break old functionality)

Screen.Recording.2023-03-29.at.8.57.02.AM.mov

Things to look for during review

• Make sure all references to iot or bx class prefix is using the prefix variable
• (React) All major areas have a data-testid attribute. New test ids should have test written to ensure they are not changed or removed.
• UI should be checked in RTL mode to ensure the proper handling of layout and text.
• All strings should be translatable.
• The code should pass a11y scans (The storybook a11y knob should show no violations). New components should have a11y test written.
• Unit test should be written and should have a coverage of 90% or higher in all areas.
• All components should be passing visual regression test. For new styles or components either a visual regression test should be written for all permutations or the base image updated.
• Changes or new components should either write new or update existing documentation.
• PR should link and close out an existing issue

[netlify]

✅ Deploy Preview for carbon-addons-iot-react ready!

Name	Link
🔨 Latest commit	651db09
🔍 Latest deploy log	https://app.netlify.com/sites/carbon-addons-iot-react/deploys/643db2a3c37e0f0008a09e06
😎 Deploy Preview	https://deploy-preview-3761--carbon-addons-iot-react.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site settings.

[erzhan-temir-mamyrov]

LGTM 👍