gcp_compute: Add vars_prefix to prefix host_vars (#49601)

* Add vars_prefix to prefix host_vars

* Set vars_prefix default to empty string

lib/ansible/plugins/inventory/gcp_compute.py

@@ -48,6 +48,9 @@ DOCUMENTATION = '''
             description:
                 - An optional service account email address if machineaccount is selected
                   and the user does not wish to use the default email.
+        vars_prefix:
+            description: prefix to apply to host variables, does not include facts nor params
+            default: ''
 '''
 
 EXAMPLES = '''
@@ -111,7 +114,10 @@ class InventoryModule(BaseInventoryPlugin, Constructable, Cacheable):
         hostname = self._get_hostname(item)
         self.inventory.add_host(hostname)
         for key in item:
-            self.inventory.set_variable(hostname, key, item[key])
+            try:
+                self.inventory.set_variable(hostname, self.get_option('vars_prefix') + key, item[key])
+            except (ValueError, TypeError) as e:
+                self.display.warning("Could not set host info hostvar for %s, skipping %s: %s" % (hostname, key, to_native(e)))
         self.inventory.add_child('all', hostname)
 
     def verify_file(self, path):