refactor: hoist OS-specific package names to role defaults

- nfs_server: nfs_package_name (nfs-utils / nfs-kernel-server)
- wireguard: wireguard_package_name (wireguard-tools / wireguard)
- tooling:   tooling_dig_package, tooling_netcat_package

Also fix tooling role structure: move tooling.yml to tasks/main.yml so
the role is actually invokable via 'role: tooling' (defaults/main.yml
is auto-loaded), and collapse the 10 individual package tasks into a
single list-based install.

roles/tooling/tasks/main.yml

@@ -0,0 +1,15 @@
+---
+- name: Install command-line tooling
+  ansible.builtin.package:
+    name:
+      - usbutils
+      - htop
+      - bottom
+      - wget
+      - ethtool
+      - iperf3
+      - vim
+      - nano
+      - "{{ tooling_dig_package }}"
+      - "{{ tooling_netcat_package }}"
+    state: present