"Timestamp" has no attribute "as_unit" [attr-defined]

[WillAyd]

I think we are missing the .as_unit method added to pd.Timestamp in 2.0

[Dr-Irv]

It's listed in the long list in #624 . But I'll keep this open if someone wants to do a PR. We need to add as_unit() to Timestamp, Timedelta, DatetimeIndex, TimedeltaIndex, and the dt accessors for Series