Support casting Date64 to Timestamp

[gruuya]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.
Currently the cast kernel supports casting from Timestamp to Date64, but not the other way around

Unsupported CAST from Date64 to Timestamp(Nanosecond, None)

Describe the solution you'd like
In principle I think there should be no problem casting back from Date64 into Timestamps with adequate unit conversions, having in mind the time resolution of Date64 (milliseconds).

Describe alternatives you've considered

Additional context

[alamb]

label_issue.py automatically added labels {'arrow'} from #3038