services-config.json: accept http(s)://<domain>.<pk>.dmsg service URLs + persist the :80 skyfwd across config regen

[0pcom]

Split from #3445 (the load-bearing http://<domain>.<pk>.dmsg resolver/proxy host-routing is done and live-verified; that issue is closed).

Narrow remainder: (a) accept the http(s)://<domain>.<pk>.dmsg URL form directly in services-config.json service entries; (b) persist the :80 skyfwd across config gen -r regen (autoconfig) — today skynet port add is a runtime RPC that survives restart but not config regen.