Changes:
- Add _GetDescriptionForUpload and _GetTitleForUpload.
- Add ensure_change_id to ChangeDescription, that ensures the
  description has a particular Change-Id.
- If more than a Change-Id was entered on new issue upload, remove
  all, and add a new one.

Change-Id: I0eae474eb07ea3036973b18571f72a80da425b21
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2101811Reviewed-by: Josip Sokcevic <sokcevic@google.com>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>