refactor(ansible): centralize inventory and variables in 'vars' directory

Signed-off-by: Tuan-Dat Tran <tuan-dat.tran@tudattr.dev>

playbooks/proxmox.yml

@@ -2,8 +2,6 @@
 - name: Run proxmox vm playbook
   hosts: proxmox
   gather_facts: true
-  vars_files:
-    - secrets.yml
   vars:
     is_localhost: "{{ inventory_hostname == '127.0.0.1' }}"
     is_proxmox_node: "{{ 'proxmox_nodes' in group_names }}"