smp server: combine messages and queue storage to optimise performance, prevent race condition when deleting queue and to avoid "orphan" messages. (#1395)

* smp server: combine queue and message store into one class (WIP)

* keep deleted queue tombstones to prevent race conditions and errors when restoring

* move store log from server to store implementations

* STMQueueStore type class

* fix store closed when messages expired, handle store writing errors

* types

* version

* fix recovery from missing write journal, tests

* version

src/Simplex/FileTransfer/Server.hs

@@ -181,6 +181,7 @@ xftpServer cfg@XFTPServerConfig {xftpPort, transportConfig, inactiveClientExpira
     stopServer = do
       withFileLog closeStoreLog
       saveServerStats
+      logInfo "Server stopped"
 
     expireFilesThread_ :: XFTPServerConfig -> [M ()]
     expireFilesThread_ XFTPServerConfig {fileExpiration = Just fileExp} = [expireFiles fileExp]