package/python-unitest-xml-reporting: new package

Based on initial work from Nicolas Carrier
<nicolas.carrier@orolia.com>, with the following additions:

- Updated to a newer version
- Added proper license file handling
- Added runtime test case
- Restricted to Python 3.x

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>