Patch nuget.config package source errors for official build (#639)

* Add upstream sources to slngen nuget feed

* Keep multiple feeds specified in nuget.config

* Add dotnet-public as a package source and move nuget.org to audit source

* Add back package source mapping

NuGet.config

@@ -12,20 +12,24 @@
   </activePackageSource>
   <packageSources>
     <clear />
-    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
-    <add key="dotnet10" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet10/nuget/v3/index.json" />
+    <add key="dotnet-public" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-public/nuget/v3/index.json" />
     <add key="dotnet-tools" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-tools/nuget/v3/index.json" />
+    <add key="dotnet10" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet10/nuget/v3/index.json" />
   </packageSources>
   <packageSourceMapping>
-    <packageSource key="nuget.org">
+    <packageSource key="dotnet-public">
       <package pattern="Microsoft.*" />
       <package pattern="*" />
     </packageSource>
-    <packageSource key="dotnet10">
+    <packageSource key="dotnet-tools">
       <package pattern="Microsoft.*" />
     </packageSource>
-    <packageSource key="dotnet-tools">
+    <packageSource key="dotnet10">
       <package pattern="Microsoft.*" />
     </packageSource>
   </packageSourceMapping>
+  <auditSources>
+    <clear />
+    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
+  </auditSources>
 </configuration>