fix(date-picker): correct deleted end range behavior

[francinelucca]

Closes #12734

Prevents end date from being deleted on datepicker change when user has not made changes to input.

Changelog

Changed

• packages/react/src/components/DatePicker/DatePicker.js: extend onChange behavior to prevent end date being deleted

Testing / Reviewing

1. Tab to the Range Datepicker
2. Type a valid date into the "Start Date"
3. Press tab (focus now moves to the "End Date" and keeps the start date)
4. Type a valid date into the "End Date"
5. Tab back to Start Date (shift + tab) -- you'll have to do it twice to get to the start date, see note below
6. Tab again to End Date (Tab)

You should still see both previously selected dates displayed in the calendar. Compare to react.carbondesignsystem.com where date gets deleted

Note

There's a "double focus" issue when tabbing off the end date after changing it manually and not pressing "enter" to trigger the change, I paired up with Taylor on this and we're fine with this behavior for now until flatpickr gets more stable upstream or we switch into a different implementation

[netlify]

✅ Deploy Preview for carbon-components-react ready!

Built without sensitive environment variables

Name	Link
🔨 Latest commit	c687c06
🔍 Latest deploy log	https://app.netlify.com/sites/carbon-components-react/deploys/63e682e70b76e000083584f4
😎 Deploy Preview	https://deploy-preview-13108--carbon-components-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.

[netlify]

✅ Deploy Preview for carbon-elements ready!

Name	Link
🔨 Latest commit	c687c06
🔍 Latest deploy log	https://app.netlify.com/sites/carbon-elements/deploys/63e682e7afec1400087da41a
😎 Deploy Preview	https://deploy-preview-13108--carbon-elements.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.

[tay1orjones]

Thanks for tackling this one! Looks great - the double focus issue is much less of a concern compared to the original bug. I think we can merge this even with that slight remaining nit and circle back to it if necessary.

[tw15egan]

It is working as expected! 🎉 ✅ 👍🏻