adding inline json output stream

[mirkoCrobu]

Motivation

closes https://github.com/bcmi-labs/orchestrator/issues/521 (check it for the full context, limitation, integration, realated issue)

Change description

• Single typed InitEvent callback (log/progress) as the only path to stdout.
• Per-layer Docker logs removed and replaced by progress aggregated globally across all images.
• Added --json-stream flag to system init, emitting JSONL with type, source, label, current, total, percent fields.
• The source field (docker/libs/platform) it will be used by the consumers (it will be used in the upgrade flow, where system init is called as a sub-process to distinguish between the update source events): I preferred to keep all the logs instead of returning just the Docker ones to avoid losing logs.
• Disk space check refactoring(GetBytesToDownload removed).

Additional Notes

Reviewer checklist

• PR addresses a single concern.
• PR title and description are properly filled.
• Changes will be merged in main.
• Changes are covered by tests.
• Logging is meaningful in case of troubleshooting.

[mirkoCrobu]

arduino-app-cli system init --json-stream

[mirkoCrobu]

arduino-app-cli system init