LPS-40873 WebRTCManager: add resetWebRTCClient() and checkWebRTCClientsPresences()

Since `somethingTime` is always a time stamp (not an interval), I used `presenceDuration` to represent an interval (difference between two times). In this regard, I think `_CONNECTION_TIMEOUT_TIME` and `_PRESENCE_TIMEOUT_TIME` should be named resp. `_CONNECTION_TIMEOUT_DURATION` and `_PRESENCE_TIMEOUT_DURATION`.