Add the ability for PDK to generate a missing unit or class spec test skeleton

When I run pdk convert i would like to see pdk parse the manifests (lib later) folder and create a unit || defined spec for each class if one does not exist from the template

I would like to see `pdk new` support `pdk new test unit || provider||defined` which generates a unit or classes test from the template for a manifest with or without (via a flag) validation the manifest or class exists