MQTTnet 2.8.0-rc4

* [Core] Performance optimizations. * [Core] Due to performance reasons the timestamp of log messages is now in UTC format. * [Core] Added several packet validations. * [Core] Log messages now contain the complete source path including parent components. * [Core] The adapter now has an _Endpoint_ definition as string containing remote IP and port. * [Client] Received messages are now processed completely in the worker thread without creating new Tasks. * [Client] Fixed wrong calculation for sending keep alive packets (thanks to @cstichlberger) * [Client] A clean disconnect (via DisconnectAsync) will no longer throw an exception. * [Client] Added new overloads for quick message publishing. * [ManagedClient] The managed client is moved to a separate nuget package. * [ManagedClient] Added an own message format with extended properties like ID (BREAKING CHANGE). * [ManagedClient] Fixed a loading issue of stored application messages (thanks to @JTrotta). * [ManagedClient] Added a new event which is fired when a synchronization of the subscriptions has failed. * [ManagedClient] Added a new event which is fired when a connection attempt has failed. * [ManagedClient] Exposed a new property which provides the count of not published messages (pending messages count). * [Server] Added support for other WebSocket sub protocol formats like mqttv-3.1.1 (thanks to @israellot). * [Server] The takeover of an existing client sessions is now treated as a _clean_ disconnect of the previous client. * [Server] The pending messages queue per client is now limited to 250 messages. Overflow strategy and count can be changed via options (thanks to @VladimirAkopyan) * [Server] Keep alive checking is now suspended while large packages are being received (and thus the client is connected). Keep alive checking continues after a large packet is received completely. * [Server] Rewritten the _ConnectedClients_ API and added new features for disconnecting and Endpoint information (IP etc.). * [Server] Added settings for disabling persistent sessions and defining a max pending messages queue size per session. * [Server] Persistent sessions are disabled by default (BREAKING CHANGE!). * [Server] Added a new interceptor which is invoked before a new message is added to the client queue. * [Server] Added support for Linux servers by dividing IPv4 and IPv6 support and adding new options (BREAKING CHANGE!). * [Server] Gracefully closed connections are no longer reported as warnings.