[ML] Update APIs that support _all to also use wildcarded parameters

[benwtrent]

Many ML APIs support _all and * as parameters to grab ALL entries in a collection.

All APIs that support _all or * for gathering data should also support comma delimited patterns (e.g. foo*,bar).

Here is a list of our APIs with incomplete support:

• GET _ml/calendars/<calendar_id>/events
• GET _ml/calendars/<calendar_id>
• GET _ml/anomaly_detectors/<job_id>/model_snapshots/<snapshot_id> (support more than one snapshot id)
• DELETE _ml/anomaly_detectors/<job_id>/_forecast/<forecast_id> (support more than one forecast id)

[elasticmachine]

Pinging @elastic/ml-core (:ml)

[benwtrent]

This is corrected in #62563