Introduce ndjson writer

Merged Nikola Milojevic requested to merge 31101-project-export-with-ndjson into master

This MR is next step to our initiative to introduce ndjson as a way to process import/export(&2734)

We introduced straming_serializer in #208803 (closed)

This MR:

  • implements a NdjsonWriter that writes ndjson using StreamingSerializer.
  • it will be based on a feature flag that can switch between fat or ndjson.
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