docs(k3d-dev): create sane coredns config for bb domains

General MR

Summary

This MR fixes a longstanding pain point with the k3d-dev script where big-bang development domains were not resolvable within the cluster without manual intervention. This was especially apparent and problematic when developers attempted to run helm test in their dev environments due to many cypress tests attempting to resolve these development domains.

With this change, helm test should now work out-of-the-box in k3d dev environments with the overlay provided in tests/test-values.yaml.

Additionally, it centralizes a lot of the domain determination logic and gives script users the ability to override the domain under test to better match their testing needs.

Relevant logs/screenshots

Passing helm test out of the box

❯ helm test -n bigbang monitoring-grafana
NAME: monitoring-grafana
LAST DEPLOYED: Tue Jan 20 18:39:44 2026
NAMESPACE: monitoring
STATUS: deployed
REVISION: 1
TEST SUITE:     allow-egress-from-monitoring-grafana-cypress-test-to-anywhere-any-port
Last Started:   Tue Jan 20 12:46:04 2026
Last Completed: Tue Jan 20 12:46:04 2026
Phase:          Succeeded
TEST SUITE:     monitoring-grafana-cypress-config
Last Started:   Tue Jan 20 12:46:03 2026
Last Completed: Tue Jan 20 12:46:04 2026
Phase:          Succeeded
TEST SUITE:     monitoring-grafana-cypress-test
Last Started:   Tue Jan 20 12:46:04 2026
Last Completed: Tue Jan 20 12:48:18 2026
Phase:          Succeeded
❯ helm test -n bigbang monitoring-monitoring
NAME: monitoring-monitoring
LAST DEPLOYED: Tue Jan 20 18:38:12 2026
NAMESPACE: monitoring
STATUS: deployed
REVISION: 1
TEST SUITE:     allow-egress-from-monitoring-monitoring-cypress-test-to-anywhere-any-port
Last Started:   Tue Jan 20 12:51:03 2026
Last Completed: Tue Jan 20 12:51:03 2026
Phase:          Succeeded
TEST SUITE:     monitoring-monitoring-cypress-config
Last Started:   Tue Jan 20 12:51:03 2026
Last Completed: Tue Jan 20 12:51:03 2026
Phase:          Succeeded
TEST SUITE:     monitoring-monitoring-cypress-test
Last Started:   Tue Jan 20 12:51:04 2026
Last Completed: Tue Jan 20 12:52:15 2026
Phase:          Succeeded
❯ helm test -n bigbang kiali-kiali
NAME: kiali-kiali
LAST DEPLOYED: Tue Jan 20 18:39:46 2026
NAMESPACE: kiali
STATUS: deployed
REVISION: 1
TEST SUITE:     allow-egress-from-kiali-kiali-cypress-test-to-anywhere-any-port
Last Started:   Tue Jan 20 12:52:23 2026
Last Completed: Tue Jan 20 12:52:23 2026
Phase:          Succeeded
TEST SUITE:     kiali-kiali-cypress-config
Last Started:   Tue Jan 20 12:52:23 2026
Last Completed: Tue Jan 20 12:52:23 2026
Phase:          Succeeded
TEST SUITE:     kiali-kiali-cypress-test
Last Started:   Tue Jan 20 12:52:23 2026
Last Completed: Tue Jan 20 12:53:30 2026
Phase:          Succeeded

EC2 /etc/hosts entries

MetalLB

ubuntu@ip-172-31-13-192:~$ cat /etc/hosts
127.0.0.1 localhost

# The following lines are desirable for IPv6 capable hosts
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts
## begin dev.bigbang.mil section (METAL_LB)
172.20.1.241 alertmanager.dev.bigbang.mil anchore-api.dev.bigbang.mil anchore.dev.bigbang.mil argocd.dev.bigbang.mil chat.dev.bigbang.mil gitlab.dev.bigbang.mil grafana.dev.bigbang.mil headlamp.dev.bigbang.mil kiali.dev.bigbang.mil kibana.dev.bigbang.mil minio-api.dev.bigbang.mil minio.dev.bigbang.mil neuvector.dev.bigbang.mil nexus.dev.bigbang.mil policyreporter.dev.bigbang.mil prometheus.dev.bigbang.mil registry.dev.bigbang.mil sonarqube.dev.bigbang.mil tempo.dev.bigbang.mil tracing.dev.bigbang.mil twistlock.dev.bigbang.mil
172.20.1.240 keycloak.dev.bigbang.mil vault.dev.bigbang.mil
## end dev.bigbang.mil section

MetalLB with additional Public IP

ubuntu@ip-172-31-12-24:~$ cat /etc/hosts
127.0.0.1 localhost

# The following lines are desirable for IPv6 capable hosts
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts
## begin dev.bigbang.mil section (METAL_LB)
172.31.12.24 alertmanager.dev.bigbang.mil anchore-api.dev.bigbang.mil anchore.dev.bigbang.mil argocd.dev.bigbang.mil chat.dev.bigbang.mil gitlab.dev.bigbang.mil grafana.dev.bigbang.mil kiali.dev.bigbang.mil kibana.dev.bigbang.mil minio-api.dev.bigbang.mil minio.dev.bigbang.mil neuvector.dev.bigbang.mil nexus.dev.bigbang.mil policyreporter.dev.bigbang.mil prometheus.dev.bigbang.mil registry.dev.bigbang.mil sonarqube.dev.bigbang.mil tempo.dev.bigbang.mil tracing.dev.bigbang.mil twistlock.dev.bigbang.mil
172.31.13.183 keycloak.dev.bigbang.mil vault.dev.bigbang.mil
## end dev.bigbang.mil section

Linked Issue

Closes #2878 (closed)

Upgrade Notices

N/A