feat(gateways) prepare ci.jenkins.io vnet for more agents (AKS) (#233)

* feat(vnets) add a new subnet for the ci.jenkins.io agents 1 AKS cluster - ref. jenkins-infra/helpdesk#2649

Signed-off-by: Damien Duportal <damien.duportal@gmail.com>

* feat(gateways) associate NAT gateway to subnet cijenkinsio_kubernetes to use it as outbound method

Signed-off-by: Damien Duportal <damien.duportal@gmail.com>

* feat(gateways) spread outbound requests through 2 public IPs instead of 1 for cijenkinsio agents (all)

Signed-off-by: Damien Duportal <damien.duportal@gmail.com>

---------

Signed-off-by: Damien Duportal <damien.duportal@gmail.com>
Co-authored-by: Hervé Le Meur <91831478+lemeurherve@users.noreply.github.com>

gateways.tf

@@ -79,9 +79,10 @@ module "ci_jenkins_io_outbound_sponsorship" {
   subnet_names = [
     azurerm_subnet.public_jenkins_sponsorship_vnet_ci_jenkins_io_agents.name,
     azurerm_subnet.ci_jenkins_io_controller_sponsorship.name,
-    ## TODO: uncomment once the subnet is created to avoid "not found" errors
-    # azurerm_subnet.ci_jenkins_io_kubernetes_sponsorship.name,
+    azurerm_subnet.ci_jenkins_io_kubernetes_sponsorship.name,
   ]
+
+  outbound_ip_count = 2
 }
 
 module "privatek8s_outbound" {