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>

Samples/Diagnostics/PackageInspection_Samples.cs

@@ -6,7 +6,7 @@
 // ReSharper disable UnusedMember.Global
 // ReSharper disable InconsistentNaming
 
-using MQTTnet.Diagnostics;
+using MQTTnet.Diagnostics.PacketInspection;
 
 namespace MQTTnet.Samples.Diagnostics;
 
@@ -17,19 +17,19 @@ public static class PackageInspection_Samples
         /*
          * This sample covers the inspection of outgoing packages from the client.
          */
-        
-        var mqttFactory = new MqttFactory();
-        
+
+        var mqttFactory = new MqttClientFactory();
+
         using (var mqttClient = mqttFactory.CreateMqttClient())
         {
             var mqttClientOptions = mqttFactory.CreateClientOptionsBuilder()
                 .WithTcpServer("broker.hivemq.com")
                 .Build();
-            
+
             mqttClient.InspectPacketAsync += OnInspectPacket;
-            
+
             await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
-            
+
             Console.WriteLine("MQTT client is connected.");
 
             var mqttClientDisconnectOptions = mqttFactory.CreateClientDisconnectOptionsBuilder()