Fix DateTimeOffset.DateTime UTC bug

[Arkatufus]

Fixes https://github.com/akkadotnet/akka.net/blame/554086ccba07338194aca2a1eb8e0f9d801973b7/src/core/Akka.Persistence/Eventsourced.cs#L221

1. It uses DateTimeOffset.Date which strips the time portion of the DateTime struct
2. DateTimeOffset.DateTime returns a DateTime object with DateTimeKind.Unspecified and we need DateTimeKind.Utc

Changes

Add a new property in ITimeProvider interface that returns a DateTime.UtcNow

Checklist

For significant changes, please ensure that the following have been completed (delete if not relevant):

• This change follows the Akka.NET API Compatibility Guidelines.
• I have reviewed my own pull request.

[Aaronontheweb]

LGTM