6.1 Preview 1 Bug reading VARBINARY

[Wraith2]

https://github.com/SergeiPavlov/SqlClientBug/

To run:
dotnet run "Server=localhost;Database=TestDb;User Id=sa;Password=password;Encrypt=False;"

If I change to synchronous cmd.ExecuteScalar() or Size = 10_000 it works correctly.

Originally posted by @SergeiPavlov in #593