Implements API for retrieval of symbols and other debug artifacts from symbol store.
Builds are available on the dotnet-tools feed:
https://dev.azure.com/dnceng/public/_artifacts/feed/dotnet-tools/NuGet/Microsoft.SymbolStore https://dev.azure.com/dnceng/public/_artifacts/feed/dotnet-tools/NuGet/Microsoft.FileFormats https://dev.azure.com/dnceng/public/_artifacts/feed/dotnet-tools/NuGet/dotnet-symbol