Microsoft.Spark nuget package shouldn't have symbols files in it

[eerhardt]

We are currently packaging the .pdb symbols file into the NuGet package. But we should be using the new .snupkg format instead.

See https://docs.microsoft.com/en-us/nuget/create-packages/symbol-packages-snupkg

The reason we don't want symbols in the NuGet package is because it bloats every application that uses this package. Symbols are only be used when debugging, so publishing an application shouldn't need them.

[rapoth]

Great point! Ideally, we'd like to have separated Debug and Release packages similar to https://github.com/dotnet/machinelearning

What do you think?