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/nats/module.json

@@ -41,6 +41,17 @@
   "guards": [
     8222
   ],
+  "data": {
+    "own": [
+      {
+        "id": "jetstream",
+        "path": "${dir:jetstream-data}",
+        "class": "valuable",
+        "active": "1d",
+        "why": "the bus's streams and key-value buckets: the hand-act log, conditions, every module's state; written all the time"
+      }
+    ]
+  },
   "resources": [
     {
       "id": "jetstream-data",