ref(autofix): Reuse the organization trace endpoint to simplify logic (#97550)

The tracing logic didn't seem to be working quite right, and it was
super complex and unmaintainable anyway to try to mold it into the old
transaction-based logic.

So this PR simplifies things by just reusing the
OrganizationTraceEndpoint, similar to the AI trace summary endpoint. On
the Seer side, we'll also need to make changes to support the new data
structure.

Seer PR: getsentry/seer#3117

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Co-authored-by: Kush Dubey <[email protected]>

Author: roaga