Rigify: Fix T80764: handling of bones with ORG prefix in raw_copy.

Originally the raw_copy rig used a standard API of rigify to rename
the bone after generate already added an ORG prefix. However, if the
bone already had that prefix, generate didn't add the second one to
avoid 'ORG-ORG', and thus raw_copy removed the only remaining prefix.

As the simplest solution, hard-code handling of this rig in generate.
This isn't that bad, because this rig is special by definition, and
the special handling consists in doing nothing.

The original API based code is kept commented out as an example.