Deleting an actor leaks its in-progress snapshot when the template is gone

ActorStatus.in_progress_snapshot_name holds only the snapshot's name, so
the delete workflow has to rebuild the storage prefix from the actor
template's snapshots_config.storage_location. If the template has been
deleted or renamed, the prefix cannot be derived: the workflow logs a
warning, skips the release, and the objects stay in the bucket forever.

Repro: suspend an actor, kill ateapi mid-checkpoint so the in-progress
name stays set, delete the template, then delete the actor. The actor
finalizes and the objects under its prefix remain.