Declare every module's data; the backup holder measures it (hq ADR 0233)

Backup lines are derived from each module's data section instead of written by hand; the holder
measures declared items, reads the array under them, and deletes a retired item only after a last
restore point; the Go providers say each held consumer's size so an empty replacement is seen.

modules/lab/module.json

@@ -5,6 +5,16 @@
     "container-runtime",
     "virtualisation"
   ],
+  "data": {
+    "own": [
+      {
+        "id": "work",
+        "path": "${dir:work}",
+        "class": "cache",
+        "why": "the lab's runs, each thrown away"
+      }
+    ]
+  },
   "resources": [
     {
       "id": "state",