[ML] Add "created_by" info for jobs to ML usage stats #38403
Description
It would be useful for the MachineLearningFeatureSetUsage information to include counts of the different values of the custom_settings.created_by field.
This will indicate which UI wizard (if any) was used to create the job.
The stats need to include a count where custom_settings.created_by is not set, or set to a value that does not correspond to the value set by any UI wizard.