Refactor & improve makeseeds

Summary:
Backport of core#16999
This patch allows for an increased number of ipv6 seeds to be recorded by automation infra and unlocks further backports for improving makeseeds in the future.

https://github.com/bitcoin/bitcoin/pull/16999/commits/301c2b1ab594c483b698fa7c3f1ed8932af0554c (improve logging and filtering)
https://github.com/bitcoin/bitcoin/pull/16999/commits/3314d879666beaa1aa724ff28ad15326167e548f (factor out ASN lookup)
https://github.com/bitcoin/bitcoin/pull/16999/commits/c254a9ef692190342aa697e2c778d90091865e95 (dedup by ip, port)
https://github.com/bitcoin/bitcoin/pull/16999/commits/ed76299bea3e067cbc835fe50ce05ea1720d61c1 (limit per network)
https://github.com/bitcoin/bitcoin/pull/16999/commits/801d341f3a4b00633aa135407752d21ba868e37b (more fancy output)

Test Plan:

python3 makeseeds.py < seeds_main.txt > nodes_main.txt
python3 makeseeds.py < seeds_test.txt > nodes_test.txt
git diff

Diff should be more additions than removals and retain most of the old entries.

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D12138