importer: Import raw sources for inetnum's again

importer: Import raw sources for inetnum's again

The extended feeds do not have enough detailed information
for us, so that we need to import inetnums from RIRs where
possible. Filtering private networks is necessary as RIR data
may contain 0.0.0.0/0 or similar entries for administrative
purposes or due to misfilings.

Special thanks goes to Michael for spending numerous hours
on this, setting up a testing environment and providing helpful
advice while debugging.

Partially fixes: #12458

Cc: Michael Tremer <michael.tremer@ipfire.org>
Signed-off-by: Peter Müller <peter.mueller@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>