agent: optimize subscriptions memory usage (#1651)

* agent: optimize subscriptions memory usage more (do not store subscribed queues in memory) WIP

* use new session subscriptions data

* version

* remove old data structure

* remove version

* batch deletions

* test TSessionSubs

* comment

src/Simplex/Messaging/Client.hs

@@ -29,6 +29,7 @@
 module Simplex.Messaging.Client
   ( -- * Connect (disconnect) client to (from) SMP server
     TransportSession,
+    SMPTransportSession,
     ProtocolClient (thParams, sessionTs),
     SMPClient,
     ProxiedRelay (..),
@@ -549,6 +550,8 @@ type UserId = Int64
 -- Please note that for SMP connection ID is used as entity ID, not queue ID.
 type TransportSession msg = (UserId, ProtoServer msg, Maybe ByteString)
 
+type SMPTransportSession = TransportSession BrokerMsg
+
 -- | Connects to 'ProtocolServer' using passed client configuration
 -- and queue for messages and notifications.
 --