Add Net9.0 to wcf client test and supress warnings due to the change. (#5666)

Author: imcarolwang

Directory.Build.props

@@ -41,8 +41,8 @@
   </ItemGroup>
 
   <PropertyGroup>
-    <ScenarioTestTargetFrameworks>net8.0</ScenarioTestTargetFrameworks>
-    <UnitTestTargetFrameworks>net8.0</UnitTestTargetFrameworks>
+    <ScenarioTestTargetFrameworks>net8.0;net9.0</ScenarioTestTargetFrameworks>
+    <UnitTestTargetFrameworks>net8.0;net9.0</UnitTestTargetFrameworks>
     <!-- This is the target framework version of the built tests picked up to send to Helix -->
     <XUnitPublishTargetFramework>net8.0</XUnitPublishTargetFramework>
   </PropertyGroup>

src/System.Private.ServiceModel/tests/Scenarios/Contract/Service/ServiceContractTests.4.0.0.cs

@@ -495,7 +495,7 @@ public static void BasicHttp_Async_Close_Proxy_WithSingleThreadedSyncContext()
 
     private static string StreamToString(Stream stream)
     {
-        stream.Read(Array.Empty<byte>(), 0, 0);
+        stream.ReadExactly(Array.Empty<byte>(), 0, 0);
         var reader = new StreamReader(stream, Encoding.UTF8);
         return reader.ReadToEnd();
     }

src/System.ServiceModel.Http/tests/ServiceModel/BasicHttpsBindingTest.cs

@@ -71,7 +71,9 @@ public static void DirectlySettingCertificateCredential()
         binding.Security.Transport.ClientCredentialType = HttpClientCredentialType.Certificate;
         var factory = new ChannelFactory<IWcfService>(binding, new EndpointAddress(FakeAddress.HttpsAddress));
         byte[] certificateBytes = Convert.FromBase64String(BasicHttpsBindingTest.AUserCertificate);
+#pragma warning disable SYSLIB0057
         var certificate = new X509Certificate2(certificateBytes);
+#pragma warning restore SYSLIB0057
         factory.Credentials.ClientCertificate.Certificate = certificate;
         var channel = factory.CreateChannel();
         Assert.Throws<PlatformNotSupportedException>(() => channel.Echo("hello"));