depot_tools: Restore third_party/upload.py

This is a partial revert of
https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1702495

It is used by my_activity.py (via rietveld)

Bug: 984745, 984182
Change-Id: Ic9a3e59a2ffb4b500666f9ad2ee076c8bb81a3d6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1703390
Reviewed-by: Andy Perelson <[email protected]>
Commit-Queue: Edward Lesmes <[email protected]>