Fix instance/ipool key naming in json output

[kobajagi]

Description

Renames keys that did not match actual data:

• template_id -> template;
• zoneid -> zone.

These were present in both c instance show and c instance-pool show commands.

Checklist

(For exoscale contributors)

• Changelog updated (under Unreleased block)
• Testing

Testing

$ go run . c i show 1d1b482c-adcf-4928-acd9-fdffbe2d7c98 --output-format json | jq                                                                                        
{                                                                                                                                                                                            
  "id": "1d1b482c-adcf-4928-acd9-fdffbe2d7c98",                                                                                                                                              
  "name": "my-instance",                                                                                                                                                                
  "creation_date": "2024-06-14 15:09:06 +0000 UTC",                                                                                                                                          
  "instance_type": "standard.medium",                                                                                                                                                        
  "template": "sks-node-1.30.jammy",                                                                                                                                                         
  "zone": "ch-gva-2",                                                                                                                                                                        
  "anti_affinity_groups": [                                                                                                                                                                  
    "my-sks-anti-affinity-group"                                                                                                                                                             
  ],                                                                                                                                                                                         
  "deploy_target": "-",                                                                                                                                                                      
  "security_groups": [                                                                                                                                                                       
    "default",                                                                                                                                                                               
    "my-sks-security-group"                                                                                                                                                                  
  ],                                                                                                                                                                                         
  "private-instance": "No",                                                                                                                                                                  
  "private_networks": [],                                                                                                                                                                    
  "elastic_ips": [],
  "ip_address": "x.x.x.x",
  "ipv6_address": "-",
  "ssh_key": "-",
  "disk_size": "50 GiB",
  "state": "running",
  "labels": null,
  "reverse_dns": ""
}