Zabbix-stg: More base server config

This adds:
- Matrix media type
- User for a Matrix bot
- Trigger using Matrix & the bot
- PSK configuration, using the PSK file already deployed
- 2 base templates
  - a general one suitable even for Koji
  - a dependant one for all other hosts
- Autoregistration config to use the new base template

This is all scoped to staging via a new include in main.yml

inventory/group_vars/zabbix_stg

@@ -21,3 +21,4 @@ num_cpus: 2
 # the host_vars/$hostname file
 tcp_ports: [80, 443]
 notes: Test instance for zabbix server
+zabbix_stg_matrix_roomid: "!dODrizXNtqWjiylAyh:fedora.im"