Deleting all entries pertaining to a particular experiment_run

This functionality might be good to make control the size of predictions table. Might also help in removing unwanted (buggy) runs altogether from the database.

Search the repository for the predictions table and experiment_run records to locate the relevant models and deletion entry points. Clarify whether deletion must cover all related records and what safeguards are required, then define completion as removing every entry for one experiment run without affecting other runs.

Written by the indexing model from the issue text.