new plugin to detect upload of an previous or existing version in Debian

There is currently no warning about packages that are uploaded with a lower or equal version to an existing package in Debian for a given distribution.

We should add a QA error for that.

Example:

uploading a hello/1.1 for unstable while Debian has a hello/1.4
uploading a hello/1.3 for buster-backports while Debian already has it

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information