[seeder] Make unreliable node reasons clear and consistent

Summary:
This is a partial backport of bchn#1820
https://gitlab.com/bitcoin-cash-node/bitcoin-cash-node/-/merge_requests/1820/diffs?commit_id=8f435c20698488125a5f4d3759f81237acebff93

Note that I don't like the work reliableness, and reliability is already used in this codebase for another concept, so I went for ReliabilityStatus

Depends on D16905

Test Plan:
run the seeder before and after this change, confirm that we get a similar number of good nodes (check for no regression)

ninja bitcoin-seeder check-seeder
src/seeder/bitcoin-seeder -dumpinterval=60

After a few minutes

awk '{ if ($2 == 1) { print } }' dnsseed.dump

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D16499