feat(scheduler): add INFO logging for dataset-triggered DagRun creation

[leossantos]

Log which DAGs are selected as dataset-triggered (with ADRQ timestamp ranges) and log successful DagRun creation with dag_id, exec_date, prev_exec, event count, and event URIs. This provides visibility into the scheduler's dataset trigger decisions for debugging premature trigger incidents.

Made-with: Cursor

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[boring-cyborg]

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