Time conversion backward compatibility

[ZepengHuo]

Imon has run into ETL issues of femr.featurizers.join_labels where there's consistent 1 day gap, so joining the features and labels will give error. Per her description, it's the time stamp conversion from FEMR v1 to always have UTC but not for v2. So presumably the labeling are done on v1 and featurization is on v2. If this is a FEMR issue then we can discuss.

From Imon:

It strange that I have 1 day difference between feature_times and label["prediction_time"].