feat(serialization): Bringing over the DataStream class from UTP with some modifications

Bringing over the DataStream class from UTP into the core repo, we remove some of the unused features as well as make it work with some already defined MLAPI types.

This class is also optimized to be used in a job context/burst context and has no managed allocations, as well thread safety.

(Original) https://github.com/Unity-Technologies/netcode/blob/master/com.unity.transport/Runtime/DataStream.cs

Author: wackoisgod