mesh-grants: take each user's hash from the vault's bus-accounts and say per user whether one is held, so take-over waits until every user has a credential

ADR 0547 clause 9: the vault writes the hash of each bus account it holds into bus-accounts.<user>. The grants part
watches that state (no timer), carries the hash with each shadow user in memory only, and its user-list tool says per
user whether a hash is held and how its line would differ from the loaded one (same, adds, left out for want of a
credential, loses its login); never the hash, since bcrypt salts make two hashes incomparable. Take-over names the
users with no hash.

Issue: 1945

modules/mesh-grants/module.json

@@ -10,7 +10,8 @@
     "mesh-delivery-builder.builds",
     "mesh-delivery-indexer.manifests",
     "mesh-delivery-indexer.modules",
-    "node-engine.have"
+    "node-engine.have",
+    "mesh-vault.bus-accounts"
   ],
   "invokes": [
     "nats.nats_streams",