Catalog: add migration for mock_authentication_nonce setting

The
(SASL/SCRAM)[MaterializeInc#33468]
PR introduces the need for some stable, cluster wide, cryptographically
random key material. We use this material to be able to present
deterministic challenges for even users that don't exist to guard
against enumeration attacks. Old versions of the catalog won't have this
so we have to add it.

Author: DAlperin

src/catalog-protos/protos/hashes.json

@@ -46,5 +46,9 @@
   {
     "name": "objects_v77.proto",
     "md5": "2dc9da6bcf13afb0db7233b26720c18f"
+  },
+  {
+    "name": "objects_v78.proto",
+    "md5": "64e78f72cd10034f91e4c034ff9e4f96"
   }
 ]