(core) limit access to list of snapshots for documents with granular access

Summary:
Snapshots can now only be listed for users with non-nuanced access
(no access rules, or owners on docs with rules). If a snapshot URL
leaks, or is shared by a user who can list snapshots, that URL
behaves as before -- it gives access to the snapshot according
to access rules in that snapshot.

Test Plan: added test

Reviewers: georgegevoian, dsagal

Reviewed By: georgegevoian, dsagal

Subscribers: jarek

Differential Revision: https://phab.getgrist.com/D3698

static/locales/en.client.json

@@ -111,6 +111,7 @@
   "DocHistory": {
     "Activity": "Activity",
     "Snapshots": "Snapshots",
+    "SnapshotsUnavailable": "Snapshots are unavailable.",
     "OpenSnapshot": "Open Snapshot",
     "CompareToCurrent": "Compare to Current",
     "CompareToPrevious": "Compare to Previous",