tools: add a get_package_provider() function, returning the package name that...

tools: add a get_package_provider() function, returning the package name that best matches the system

This function uses distro.like() to obtain a list of distributions
similar to the one we are running on.
It means that we will, for example, be able to suggest Debian packages
when running under Ubuntu.

Gbp-Dch: Short
Signed-off-by: Mattia Rizzolo <mattia@debian.org>