Merge pull request #7986 from jtattermusch/coreclr_interop_fixes

src/csharp/Grpc.Auth/Grpc.Auth.csproj

src/csharp/Grpc.Auth/packages.config

src/csharp/Grpc.Auth/project.json

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

...harp/Grpc.HealthCheck.Tests/Grpc.HealthCheck.Tests.csproj

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

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

src/csharp/Grpc.HealthCheck/packages.config

src/csharp/Grpc.HealthCheck/project.json

...ationTesting.Client/Grpc.IntegrationTesting.Client.csproj

src/csharp/Grpc.IntegrationTesting.Client/packages.config

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

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