feat(nr): serde for signed ints

[Maddiaa0]

Overview

Adds serde for signed integer types (and the missing u16), from #9179

Just adds litle smoke tests for the stuff I've added at the bottom of the file, I can add for all if deemed required

@Cheetah0x discussed with @vezenovm - let me know if there are other places this needs to be added for the change to take effect - just followed instructions here