Improve performance and drop support for old frameworks (#2068)

* Remove WebSocket4Net extension library

* Remove UWP support

* Drop support for all old frameworks

* Update CI

* Update CI

* Update CI

* Update CI

* Remove obsolete code

* Set default protocol version to 5.0.0

* Remove obsolete tests

* Remove old dependencies

* Reset release notes

* Move server to dedicated project

* Fix unit tests

* Update and cleanup nuget packages

* Fix unit tests
Refactor code

* No longer throw exception when receiving non success CONNACK

* Enable nuget signing

* Enable nuget signing

* Enable nuget signing

* Enable nuget signing

* Enable nuget signing

* Enable nuget signing

* Enable nuget signing

* Enable nuget signing

* Enable code signing

* Enable code signing

* Enable code signing

* Fix client endpoint handling

* Improve CI

* Fix CI

* Fix CI

* Fix CI

* Fix CI

* Import changes from version 4

* Cleanup target frameworks and remove obsolete code

* Drop support for dotnet7.0

* Remove managed client

* Version5 auditmode (#2016)

Added NuGet audit mode and some other settings to get informed about security issues.

* Address warnings from analyzers

* Support for ReadOnlySequence as payload (#2046)

* use ReadOnlySequence as payload

* fix build

* fix build

* skip sign in forks

* remove unnecessary owner

* tests and extensions

* remove test

* simplify WritePacketBuffer, remove unused helper

* Adjust namespaces

* Fix build errors

* Import latest fixes from main branch

* Adjust namespaces

---------

Co-authored-by: SeppPenner <HansM2013@gmx.de>
Co-authored-by: Martin Regen <mregen@microsoft.com>

Source/MQTTnet.TestApp/MessageThroughputTest.cs

@@ -1,4 +1,3 @@
-using MQTTnet.Client;
 using MQTTnet.Server;
 using System.Collections.Generic;
 using System;
@@ -77,8 +76,9 @@ namespace MQTTnet.TestApp
             new TopicGenerator().Generate(NumPublishers, NumTopicsPerPublisher, out _topicsByPublisher, out _singleWildcardTopicsByPublisher, out _multiWildcardTopicsByPublisher);
 
             var serverOptions = new MqttServerOptionsBuilder().WithDefaultEndpoint().Build();
-            var factory = new MqttFactory();
-            _mqttServer = factory.CreateMqttServer(serverOptions);
+            var mqttClientFactory = new MqttClientFactory();
+            var mqttServerFactory = new MqttServerFactory();
+            _mqttServer = mqttServerFactory.CreateMqttServer(serverOptions);
             await _mqttServer.StartAsync();
 
             Console.WriteLine();
@@ -90,7 +90,7 @@ namespace MQTTnet.TestApp
             foreach (var pt in _topicsByPublisher)
             {
                 var publisherName = pt.Key;
-                var mqttClient = factory.CreateMqttClient();
+                var mqttClient = mqttClientFactory.CreateMqttClient();
                 var publisherOptions = new MqttClientOptionsBuilder()
                     .WithTcpServer("localhost")
                     .WithClientId(publisherName)
@@ -106,7 +106,7 @@ namespace MQTTnet.TestApp
             _mqttSubscriberClients = new List<IMqttClient>();
             for (var i = 0; i < NumSubscribers; ++i)
             {
-                var mqttClient = factory.CreateMqttClient();
+                var mqttClient = mqttClientFactory.CreateMqttClient();
                 var subsriberOptions = new MqttClientOptionsBuilder()
                     .WithTcpServer("localhost")
                     .WithClientId("sub" + i)