refactor(virtualization): extract shared Xen disk definitions

roles/virtualization/tasks/_xen_disks.yml

@@ -0,0 +1,26 @@
+---
+- name: Build Xen disk definitions
+  when: virtualization_xen_disks is not defined
+  block:
+    - name: Compute Xen disk configuration
+      ansible.builtin.set_fact:
+        virtualization_xen_disks: "{{ virtualization_xen_disks | default([]) + [_xen_disk_cfg] }}"
+      vars:
+        device_letter_map: "{{ disk_letter_map }}"
+        device_letter: "{{ device_letter_map[ansible_loop.index0] }}"
+        _xen_disk_cfg: >-
+          {{
+            {
+              'path': (
+                virtualization_xen_disk_path ~ '/' ~ hostname ~ '.qcow2'
+                if ansible_loop.index0 == 0
+                else virtualization_xen_disk_path ~ '/' ~ hostname ~ '-disk' ~ ansible_loop.index0 ~ '.qcow2'
+              ),
+              'target': 'xvd' ~ device_letter,
+              'size': (item.size | float)
+            }
+          }}
+      loop: "{{ system_cfg.disks }}"
+      loop_control:
+        label: "{{ item | to_json }}"
+        extended: true