Improve speed of outcome count per threshold

[gabegma]

Description:

I tested and it’s actually faster to call compute_on_dataset_split() for Outcomes, so we don't need to wait for the tasks to be scheduled. This is the case because we call Outcomes many times with different thresholds. See the difference in the profiling logs.
logs_compute_on_ds_split.txt
logs_get_task.txt

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[JosephMarinier]

🤯