relative imports: move zabbix-repo, remove all others

zabbix-agent/meta/main.yml

 ---
 dependencies:
-  - role: zabbix-repo
+  - role: zabbix/zabbix-repo

zabbix-frontend/meta/main.yml

 ---
 dependencies:
-  - role: zabbix-repo
-  - role: webserver
-  - { role: php-fpm, fpm_pool: zabbix, fpm_user: zabbix, fpm_group: zabbix, fpm_socket_user: zabbix, fpm_socket_group: www-data, fpm_params: { date.timezone: "Europe/Berlin", post_max_size: "16M", max_execution_time: 300, max_input_time: 300, always_populate_raw_post_data: -1 } }
-# TODO webserver fails ansible on initial deployment currently by purpose
+  - role: zabbix/zabbix-repo

zabbix-proxy/meta/main.yml

 ---
 dependencies:
-  - role: zabbix-repo
+  - role: zabbix/zabbix-repo

zabbix-server/meta/main.yml

 ---
 dependencies:
-  - role: zabbix-repo
+  - role: zabbix/zabbix-repo