feat(ansible): add hold_slayer database variables and deployment

- Add hold_slayer_db_* variables to portia host_vars
- Update postgresql deploy.yml to create user, database,
  and enable extensions for hold_slayer

ansible/inventory/host_vars/portia.incus.yml

@@ -53,6 +53,9 @@ daedalus_db_password: "{{ vault_daedalus_db_password }}"
 mnemosyne_db_name: mnemosyne
 mnemosyne_db_user: mnemosyne
 mnemosyne_db_password: "{{ vault_mnemosyne_db_password }}"
+hold_slayer_db_name: hold_slayer
+hold_slayer_db_user: hold_slayer
+hold_slayer_db_password: "{{ vault_hold_slayer_db_password }}"
 
 # PostgreSQL admin password
 postgres_password: "{{ vault_postgres_password }}"