Extend update-tzdata.py to create distro files

update-tzdata.py now generates distro files into
system/timezone/output_data/distro by using
create-distro.py.

Addition of the resulting generated distro file (that
matches the other input / output files) currently
checked in.

This commit also contains the following changes:
1) Changed TimeZoneDistroBuilder to set a timestamp on
each entry in the distro .zip to make the file more
deterministic (enabling the file to be regenerated without
creating a diff).
2) Minor import fixes for .py files

Bug: 31008728
Test: Ran update-tzdata.py and confirmed the output of existing
  files is unchanged.

Change-Id: I28e559c62527a7a6b7c90838fa67d764e39d3b6f