Tag files that are whitedouts as "white-out" in container scans

[pombredanne]

We should tag files that are "whited-outs" as "white-out" in container scans so that we can possibly treat as less risky packages that are "whited-outs" as less likely to be used at run time.

[pombredanne]

Ways to do this could be one of these:

1. Add a new "tag" model and relate it to CodebaseResource using taggit like for projects

   scancode.io/scanpipe/models.py

   Line 576 in 07a0022

   labels = TaggableManager(through=UUIDTaggedItem, ordering=["name"])

2. Or add a new boolean flag is_hidden in the FileClassifierFieldsModelMixin for Resource