Fix: include lts flag in per-event product_map so TestHub derives origin correctly

[MihirR-BS]

Summary

• Build-create's product_map correctly carries `lts: true` when the session is Load Testing (see `getProductMapForBuildStartCall` in `src/testObservability.js` at ~line 1014), but the per-event send at `src/testObservability.js:529-532` (used for `TestRunStarted`/`TestRunFinished`) does not.
• Without `lts: true` on the per-event product_map, TestHub's downstream `getOriginFromSource` returns `UnknownGrid` for the event, the error rows land with `error_cluster_id=NULL`, and the Load Testing product's Unique Errors panel renders empty even when the test actually failed.
• Mirrors the equivalent Python SDK fix pattern.

Test plan

• Nightwatch load test with a failing case — Unique Errors panel now populates (previously empty).
• Non-LTS Nightwatch run unaffected — `isLoadTestingSession()` returns false, product_map.lts is `false`, no behavior change for regular Automate / Observability runs.