refactor: Move to parsing JSON for better reliablity + prep for slurmrestd

[Antvirf]

Very much WIP

• Autogenerate Slurm JSON models from openapi schemas
• Implement commands + parsers using --json
• Potentially rethink large parts of how we model data internally, current structures are all about "tables" which is no longer the case in a json-first world

[Antvirf]

yolo @copilot can you have a look at this - we'd want to go from parsing strings to parsing JSON output from slurm binary commands instead. For future proofing, we'd want to draw a very clear line between:

• 'getting' the JSON - right now just a slurm binary call, but in the future could be REST, or even from a file
• parsing the JSON into our internal structure

Secondly, our internal data structure here probably needs a rethink, can you explore this a bit and suggest 3-5 different ways to approach this?

[Copilot]

@Antvirf I've opened a new pull request, #52, to work on those changes. Once the pull request is ready, I'll request review from you.