net: split up addresses/ban dumps in preparation for moving them

Summary: his is a partial backport of Core PR14605 : https://github.com/bitcoin/bitcoin/pull/14605/commits/83c1ea2e5e66b8a83072e3d5ad6a4ced406eb1ba

Test Plan:

make check

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Subscribers: jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D4101