Add Alien::Util, and move version_cmp there

[plicease]

This PR adds an Alien::Util module for things that are needed by both the Alien::Base runtime and Alien::Build build-time without either having to depend on the other. So far the only function is version_cmp, which used to live in Alien::Base as a class method, but was used in some of the probe plugins with #300

• [x] Add actual tests in t/alien_util.t