Use kotlinx serialization instead of manual json encode/decode

[Doomsdayrs]

Description

While this might have some extremely minor losses in performance, it makes up for this fact by making it far more easy to work with.

I also placed them into their own directories to clean up the codebase.

Type of PR

• [x] Feature implementation
• [x] Refactor of code (without functional changes)

Testing

Ensure that the data classes produced match the expected JSON content.