Split 'offline' assert into their own role

The preinstall assert cover a number of things, many of which depends
only on the inventory, and can be run without any ansible_facts
collected.

Split them off to simplify re-ordering.

playbooks/boilerplate.yml

@@ -30,6 +30,13 @@
         key: "{{ (group_names | intersect(item.value) | length > 0) | ternary(item.key, '_all') }}"
       loop: "{{ group_mappings | dict2items }}"
 
+- name: Check inventory settings
+  hosts: all
+  gather_facts: false
+  tags: always
+  roles:
+    - validate_inventory
+
 - name: Install bastion ssh config
   hosts: bastion[0]
   gather_facts: false