Is your feature request related to a problem? Please describe.

I'm running weaver in CI with popen and it would be great to communicate with it using stdout / stderr without touching the filesystem. The current --format=json option outputs a stream of json object, e.g.:

{
  "...": ...
}
{
  "..": ...
}

Which are harder to parse since the whole output is not a valid json document.

Describe the solution you'd like

Providing a json lines (https://jsonlines.org) formatter that is using newline as document separator would make it easier to consume it, e.g.:

{"...": ...}
{"...": ...}

Describe alternatives you've considered

I've tried --output but looks like there's a race condition there between the different signals, e.g. metrics override traces.

Additional context
Add any other context or screenshots about the feature request here.

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