DateTimeOffset Offset is not preserved

[JoshLove-msft]

This issue is for a: (mark with an x)

- [x] bug report -> please search issues before submitting
- [ ] feature request
- [ ] documentation issue or request
- [ ] regression (a behavior that used to work and stopped in a new release)

Minimal steps to reproduce

Publish an EventGridEvent with a DateTimeOffset property within the Data object. View the event in Event Grid Viewer. The Offset is not preserved and instead a DateTime is shown in UTC.

Expected/desired behavior

The string value of the field should be shown by using the DateParseHandling setting when deserializing JSON.

Mention any other details that might be useful

Azure/azure-sdk-for-net#19859

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