NET FX and NET core uses different serializer for classes implementing the ISerializable interface

[Arkatufus]

Version Information
Version of Akka.NET? All
Which Akka.NET Modules? Akka.Serialization.Hyperion

Describe the bug
NET Framework build uses Microsoft System.Runtime.Serialization to serialize classes inheriting the ISerializable interface but uses Hyperion POCO object serializer in NET Core, making cross platform serialization impossible.

This is caused by a byte rot in the multi platform compiler directive that hasn't been updated since System.Runtime.Serialization was supported in netstandard2.0, need to synchronize .NET FX and .NET Core code.

To Reproduce
Steps to reproduce the behavior:
Reproduction repo: https://github.com/t-l-k/BrokenAkkaSerialization

Expected behavior
.NET FX and Core should use the same serializer for classes inheriting the ISerializable interface

Actual behavior
It doesn't