Add method for propagating python dependencies

An NSO package using Python might have dependencies. If we build packages on separate repos and then want to include them in another NID system repo then we won't get the dependencies of the included packages as they are not contained within the package itself - they rely on the system python to have them.

Right now, someone would have to manually keep track of this by inspecting the various included NSO packages, capturing the dependencies and writing to a requirements.txt or similar in the main NSO system repo doing composition.

We need a way to capture those dependencies.