Merge pull request #7623 from apolcyn/sys_inter_with_nuget

src/csharp/Grpc.Core.Tests/Grpc.Core.Tests.csproj

src/csharp/Grpc.Core.Tests/packages.config

src/csharp/Grpc.Core/Grpc.Core.csproj

src/csharp/Grpc.Core/Grpc.Core.nuspec

src/csharp/Grpc.Core/packages.config

src/csharp/Grpc.Core/project.json

src/csharp/Grpc.Examples.MathClient/project.json

src/csharp/Grpc.Examples.MathServer/project.json

src/csharp/Grpc.Examples.Tests/Grpc.Examples.Tests.csproj

src/csharp/Grpc.Examples.Tests/packages.config

src/csharp/Grpc.Examples/Grpc.Examples.csproj

src/csharp/Grpc.Examples/packages.config

src/csharp/Grpc.Examples/project.json

src/csharp/Grpc.HealthCheck/Grpc.HealthCheck.csproj

src/csharp/Grpc.HealthCheck/Grpc.HealthCheck.nuspec

src/csharp/Grpc.HealthCheck/packages.config

src/csharp/Grpc.IntegrationTesting.QpsWorker/project.json

src/csharp/Grpc.IntegrationTesting.StressClient/project.json

...rp/Grpc.IntegrationTesting/Grpc.IntegrationTesting.csproj

src/csharp/Grpc.IntegrationTesting/packages.config