connectionmanager: improve portability of string to integer conversion

On Windows using MSC, unsigned long is 32 bits even on 64-bit systems, while unsigned long long is 64 bits.

This commit replaces the call to std::stoul with std::stoull which should be portable.

This will address the following Jami-client issue:
jami-client-qt#1419

Change-Id: I9f7998573f493f479b9f97bf5d56ef65b8b58f57

src/connectionmanager.cpp

@@ -54,7 +54,7 @@ std::pair<dhtnet::DeviceId, dht::Value::Id> parseCallbackId(std::string_view ci)
     std::string_view vidString = ci.substr(sep + 1);
 
     dhtnet::DeviceId deviceId(deviceIdString);
-    dht::Value::Id vid = std::stoul(std::string(vidString), nullptr, 10);
+    dht::Value::Id vid = std::stoull(std::string(vidString), nullptr, 10);
     return {deviceId, vid};
 }