Test Code Improvements

In `Experimental.System.Messaging.Test.csproj`, we upgraded .NET Core 2.0 to .NET 8.0 and updated the test-related package versions to the latest.

In `QueueClientTest.cs`, we modified the function to check for the existence of a queue and create one if necessary, ensuring test independence. We also separated the queue path into a variable for improved readability.

Author: rkttu

Experimental.System.Messaging.Test/Experimental.System.Messaging.Test.csproj

@@ -1,15 +1,15 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netcoreapp2.0</TargetFramework>
+    <TargetFramework>net8.0</TargetFramework>
 
     <IsPackable>false</IsPackable>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.5.0" />
-    <PackageReference Include="MSTest.TestAdapter" Version="1.2.0" />
-    <PackageReference Include="MSTest.TestFramework" Version="1.2.0" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.0.1" />
+    <PackageReference Include="MSTest.TestAdapter" Version="4.0.2" />
+    <PackageReference Include="MSTest.TestFramework" Version="4.0.2" />
   </ItemGroup>
 
   <ItemGroup>

Experimental.System.Messaging.Test/QueueClientTest.cs

@@ -22,7 +22,14 @@ public void SendMessage()
         [TestMethod]
         public void ReceiveMessage()
         {
-            MessageQueue messageQueue = new MessageQueue(".\\Private$\\myQueue");
+            string path = ".\\Private$\\myQueue";
+            // Ensure the queue exists to make test independent
+            if (!MessageQueue.Exists(path))
+            {
+                MessageQueue.Create(path);
+            }
+
+            MessageQueue messageQueue = new MessageQueue(path);
             messageQueue.Formatter = new XmlMessageFormatter(new Type[1]
             {
                 typeof(Order)