staging: Rework output to display a summary on nodes

Created or not, this displays the output:

terraform apply
proxmox_vm_qemu.gateway: Refreshing state... (ID: orsay/qemu/109)
proxmox_vm_qemu.node: Refreshing state... (ID: orsay/qemu/114)
proxmox_vm_qemu.node: Refreshing state... (ID: orsay/qemu/115)

Apply complete! Resources: 0 added, 0 changed, 0 destroyed.

Outputs:

Apply complete! Resources: 0 added, 0 changed, 0 destroyed.

Outputs:

db0_summary =
hostname: db0
fqdn: db0.internal.staging.swh.network
network: ip=192.168.128.3/24,gw=192.168.128.1 macaddr=3A:65:31:7C:24:17

storage0_summary =
hostname: storage0
fqdn: storage0.internal.staging.swh.network
network: ip=192.168.128.2/24,gw=192.168.128.1 macaddr=CA:73:7F:ED:F9:01

Test Plan

terraform init
terraform plan

Depends on !34 (closed)

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Migrated from D1808 (view on Phabricator)