Memory optimization of StateDiff.bytes() to only use 1 new byte array instead of stateMap.size * 2 arrays

[achabill]

Description

Performance optimization of StateDiff#bytes to only use 1 new byte array instead of stateMap.size * 2 arrays.

Fixes #603

Type of change

• Enhancement (a non-breaking change which adds functionality)

Checklist:

• My code follows the style guidelines for this project
• I have performed a self-review of my own code
• I have commented on my code, particularly in hard-to-understand areas

[GalRogozinski]

Thanks!