feat: write json file with artifacts context

[shadows-withal]

Serializes the artifacts context to JSON and writes it to disk, under <dist_dir>/artifacts.json.

Lingering things

• Do we want to stick with this path? Do we want to make it customizable? - maybe later
• Do we want to give an option to disable generating this? - maybe later
• Do we want an oranda flag that only generates this file (and other relevant artifacts files like the installer txt files) - yes, done
• Are we happy with this simplistic version keeping (format_version, in integrations you'd check if your version > format version) - we track oranda versions instead

[shadows-withal]

Closes #584