Improvement: Include generator version in generated files

[theunrepentantgeek]

To allow code generation issues to be correctly traced back to the responsible version of the code generator, we desire for the files to be stamped with the version of the generator.

Marking all files would result in all files showing as changed when regenerated, which isn't good for tracking actual changes. Instead, let's embed the code generator version in the groupversion_info.go. file