Consider removing dependency 'udatetime'

[nrejac]

In idb/data_api/v2_download.py, there are three function calls using the udatetime module. This module will not build under Python 3.9 (see: freach/udatetime#32) and hasn't been updated in 3 years.

Consider eliminating this dependency. Using the standard Python datetime is an option but this will incur a performance (speed) hit.

[danstoner]

Moving this to a future python label since it is not needed for the "python 3 conversion" project.