Remove the implementation of CNetAddr from the seeder to use the one from netaddr.h

Summary: As per title. Also rename CService and associated classes from the seeder to avoid name clashes.

Test Plan:

make check

Run the seeder.

Reviewers: sickpig, schancel, #bitcoin_abc

Reviewed By: schancel, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D718