refactor(ansible): restructure inventory and remove postgres role

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

group_vars/k3s/vars.yml

@@ -1,11 +1,3 @@
-db:
-  default_user:
-    user: "postgres"
-  name: "k3s"
-  user: "k3s"
-  password: "{{ vault_k3s.postgres.db.password }}"
-  listen_address: "{{ k3s.db.ip }}"
-
 k3s:
   net: "192.168.20.0/24"
   server:
@@ -24,5 +16,3 @@ k3s:
       - 192.168.20.25
       - 192.168.20.26
       - 192.168.20.27
-
-k3s_db_connection_string: "postgres://{{ db.user }}:{{ db.password }}@{{ k3s.db.ip }}:{{ k3s.db.default_port }}/{{ db.name }}"