Bug 1962099 - QM: Restore metadata when unexpected reserved data is detected; r=dom-storage-reviewers,asuth

Update the origin metadata loading logic to detect and reject unexpected
reserved data. If unexpected data is present, the metadata file is treated as
incompatible, and restoration is triggered to ensure a consistent and valid
state.

This change protects both older and newer builds:
- Older builds won’t misinterpret new metadata written by newer builds
  (although the chance of that is quite low).
- Newer builds won’t incorrectly trust metadata files that were upgraded, then
  used by an older build, and used again, which is more likely and could lead
  to subtle or serious inconsistencies.

Differential Revision: https://phabricator.services.mozilla.com/D246936

dom/quota/ActorsParent.cpp

@@ -3546,7 +3546,9 @@ Result<FullOriginMetadata, nsresult> QuotaManager::LoadFullOriginMetadata(
 
   QM_TRY_INSPECT(const bool& reservedData1,
                  MOZ_TO_RESULT_INVOKE_MEMBER(binaryStream, Read32));
-  Unused << reservedData1;
+  if (reservedData1 != 0) {
+    QM_TRY(MOZ_TO_RESULT(false));
+  }
 
   // XXX Use for the persistence type.
   QM_TRY_INSPECT(const bool& reservedData2,