change layout for better management

- instead of just `syspkgs` and `srcpkgs` add more lists
  - `appimages`, `flatpkgs` and others as they come up

vars/zig.yml

@@ -1,5 +1,5 @@
 # vim: set filetype=yaml.ansible :
 ---
 version: 0.13.0
-install_prefix: "{{ default_config.install_prefix }}"
+install_prefix: "{{ default_install_prefix }}"
 install_path: /opt/zig