Improve circular refs handling

[P0lip]

Addresses https://datawire.slack.com/archives/C01PUJXR6CT/p1738607830906789

Summary

We already had code in place for rebundling in getHttpOperationsFromSpec function, so I made an effective use of that (on a side note - this code was pretty much no-op as things stood, the only thing it did was rewriting the top-level refs)
I considered using deference with circular="ignore", but the results were rather similar as far as the negotiated content is concerned (arguably the output prior to this change was slightly better for circular structures, as we kept at least a single copy and then left a hole). That said, I might still change it to that, as it's likely to be faster.

I tried not to touch json-schema-ref-parser (to avoid needing to fork it), but I'll have a look at some point.

Checklist

• The basics
  • I tested these changes manually in my local or dev environment
• Tests
  • Added or updated
  • N/A
• Event Tracking
  • I added event tracking and followed the event tracking guidelines
  • N/A
• Error Reporting
  • I reported errors and followed the error reporting guidelines
  • N/A

Screenshots