Separating different kind of paragraphs should be moved into debian_inspector

In scancode-toolkit, at src/packagedcode/debian_copyright.py there's the `DebianCopyrightParagraphs` clas which basically extends `DebianCopyright` at debian_inspector/copyright.py to also handle seperating the different types of paragraph in functional groups to be then used for parsing and copyright/license detection.

This should be moved to debian_inspector/copyright.py as it only extends functionality of the `DebianCopyright` class.

https://github.com/nexB/scancode-toolkit/blob/2390-improve-debian-license-detection/src/packagedcode/debian_copyright.py#L739