C#: Use NuGet package generated stubs for dependencies for flow summaries test

Author: michaelnebel

csharp/ql/test/library-tests/dataflow/library/options

@@ -1 +1,3 @@
-semmle-extractor-options: /r:System.Net.dll /r:System.Web.dll /r:System.Net.HttpListener.dll /r:System.Collections.Specialized.dll /r:System.Private.Uri.dll /r:System.Runtime.Extensions.dll /r:System.Linq.Parallel.dll /r:System.Collections.Concurrent.dll /r:System.Linq.Expressions.dll /r:System.Collections.dll /r:System.Linq.Queryable.dll /r:System.Linq.dll /r:System.Collections.NonGeneric.dll /r:System.ObjectModel.dll /r:System.ComponentModel.TypeConverter.dll /r:System.IO.Compression.dll /r:System.IO.Pipes.dll /r:System.Net.Primitives.dll /r:System.Net.Security.dll /r:System.Security.Cryptography.Primitives.dll /r:System.Text.RegularExpressions.dll ${testdir}/../../../resources/stubs/System.Web.cs /r:System.Runtime.Serialization.Primitives.dll
+semmle-extractor-options: /nostdlib /noconfig
+semmle-extractor-options: --load-sources-from-project:${testdir}/../../../resources/stubs/_frameworks/Microsoft.NETCore.App/Microsoft.NETCore.App.csproj
+semmle-extractor-options: ${testdir}/../../../resources/stubs/System.Web.cs