BinaryFormatter is obsolete in .NET 5.0 (warning issued)

[zvonimir]

This is the warning we get after switching to .NET 5.0:

/home/vagrant/corral/source/Corral/Driver.cs(1266,17): warning SYSLIB0011: 'BinaryFormatter.Serialize(Stream, object)' is obsolete: 'BinaryFormatter serialization is obsolete and should not be used. See https://aka.ms/binaryformatter for more information.' [/home/vagrant/corral/source/Corral/Corral.csproj]
/home/vagrant/corral/source/Corral/CBADriver.cs(461,35): warning SYSLIB0011: 'BinaryFormatter.Deserialize(Stream)' is obsolete: 'BinaryFormatter serialization is obsolete and should not be used. See https://aka.ms/binaryformatter for more information.' [/home/vagrant/corral/source/Corral/Corral.csproj]
/home/vagrant/corral/source/Corral/CBADriver.cs(491,17): warning SYSLIB0011: 'BinaryFormatter.Serialize(Stream, object)' is obsolete: 'BinaryFormatter serialization is obsolete and should not be used. See https://aka.ms/binaryformatter for more information.' [/home/vagrant/corral/source/Corral/Corral.csproj]

Everything still works, but it would be good to clean this up at some point.