Use latest language features (#2176)

* Make use of language features line AsyncDispose, init etc.

* Fix build errors

* Improve Unit Tests

* Improve Unit Tests

* Improve Unit Tests

* Update samples

* Remove obsolete benchmarks

* Code cleanup

* Improve unit tests

* Improve Unit Tests

* Fix Unit Tests

* Improve Unit Tests

* Improve Unit Tests

* Restore unit tests

* Exclude load tests from unit tests

Source/MQTTnet.Tests/MqttPacketWriter_Tests.cs

@@ -5,30 +5,30 @@
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using MQTTnet.Formatter;
 
-namespace MQTTnet.Tests
+namespace MQTTnet.Tests;
+
+// ReSharper disable InconsistentNaming
+[TestClass]
+public class MqttPacketWriter_Tests
 {
-    [TestClass]
-    public class MqttPacketWriter_Tests
+    protected virtual MqttBufferWriter WriterFactory()
     {
-        protected virtual MqttBufferWriter WriterFactory()
-        {
-            return new MqttBufferWriter(4096, 65535);
-        }
-
-        [TestMethod]
-        public void WritePacket()
-        {
-            var writer = WriterFactory();
-            Assert.AreEqual(0, writer.Length);
-
-            writer.WriteString("1234567890");
-            Assert.AreEqual(10 + 2, writer.Length);
-
-            writer.WriteBinary(new byte[300]);
-            Assert.AreEqual(300 + 2 + 12, writer.Length);
-
-            writer.WriteBinary(new byte[5000]);
-            Assert.AreEqual(5000 + 2 + 300 + 2 + 12, writer.Length);
-        }
+        return new MqttBufferWriter(4096, 65535);
     }
-}
+
+    [TestMethod]
+    public void WritePacket()
+    {
+        var writer = WriterFactory();
+        Assert.AreEqual(0, writer.Length);
+
+        writer.WriteString("1234567890");
+        Assert.AreEqual(10 + 2, writer.Length);
+
+        writer.WriteBinary(new byte[300]);
+        Assert.AreEqual(300 + 2 + 12, writer.Length);
+
+        writer.WriteBinary(new byte[5000]);
+        Assert.AreEqual(5000 + 2 + 300 + 2 + 12, writer.Length);
+    }
+}