Dual-write ENC data into encapi alongside Cobbler

Seed encapi (statuses, roles, prodnxsr node assignments) and make the
instance module also create an encapi_node for every VM, so the k8s
puppetserver ENC can cut over from Cobbler. Cobbler/puppetca/puppetdb
resources are left untouched.

- Add config/encapi leaf + modules/encapi driving statuses/roles/nodes
  from YAML (3 statuses, 51 roles, 13 prodnxsr physical nodes).
- Add encapi_node to modules/instance (certname, role, environment).
- Wire encapi provider into root.hcl required_providers and the module
  providers; plumb ENCAPI_WRITE_TOKEN via Makefile vault_env.

modules/encapi/providers.tf

@@ -0,0 +1,10 @@
+provider "encapi" {
+  endpoint = var.encapi_endpoint
+  # token defaults to the ENCAPI_WRITE_TOKEN environment variable
+}
+
+variable "encapi_endpoint" {
+  description = "The encapi server base URL."
+  type        = string
+  default     = "https://encapi.k8s.syd1.au.unkin.net"
+}