Dry run migration failure report

[rudolf]

If a dry-run migration (#55404) fails, generate a migration report to make it easy to create a support request:
1. The report would be a NDJSON export of all failed objects.
2. If support receives such a report, we could modify all the objects to ensure the migration would pass and send this back to the client.
3. The client can then import the updated objects using the standard Saved Objects NDJSON import and run another dry run to verify all problems have been fixed.

Part of #52202

[elasticmachine]

Pinging @elastic/kibana-platform (Team:Platform)

[rudolf]

In our experience, corrupt saved objects have always been created through writing directly to the .kibana index instead of using the saved objects API. And in all the support cases, these corrupt documents were part of testing so the best resolution was to delete them instead of trying to fix them.