Consume .NET daily builds

Update to the latest daily build of .NET 9.

Author: martincostello

NuGet.config

@@ -2,9 +2,13 @@
 <configuration>
   <packageSources>
     <clear />
+    <add key="dotnet9" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet9/nuget/v3/index.json" />
     <add key="NuGet" value="https://api.nuget.org/v3/index.json" />
   </packageSources>
   <packageSourceMapping>
+    <packageSource key="dotnet9">
+      <package pattern="*" />
+    </packageSource>
     <packageSource key="NuGet">
       <package pattern="*" />
     </packageSource>