fix: wan address isn't used by peering token

[huikang]

Description

Use wan address in the peering token.

Testing & Reproduction steps

With the following agent config,

{
   bind_addr =  “172.16.1.10”
   advertise_addr_wan = “192.168.1.10"
}
ports {
  grpc_tls = 8502
  serf_wan = 8302
},

the generated token always has the private bind address in "ServerAddresses":["172.16.1.10:8502"]," , which prevents the peering cluster from reaching the acceptor cluster.

Links

fix #15051

PR Checklist

• updated test coverage
• external facing docs updated
• not a security concern

[quinndiggitypolymath]

Just a note - I don't make use of advertise_addr_wan_ipv6 (ipv6.disable=1), but others may; what should the preference/priority be between advertise_addr_wan, advertise_addr_wan_ipv4, and advertise_addr_wan_ipv6?

[freddygv]

That's a good question, will see about how that preference could be communicated in a follow-up PR.

For now will defer to the parsed TaggedAddressWAN, which could be IPv6.