[feature request] _canceled parameter for some cleanup tasks

[civitaspo]

Hi all,

I have a feature request. I want _canceled parameter for some cleanup tasks.

When a workflow is canceled, we cannot hook any tasks currently. Sometimes I define a stateful workflow that cannot be defined by one task like using temporary storage. I want to clean up the storage in any case.

ref. https://github.com/treasure-data/digdag/blob/29ef4c68e719940c940b9fdcc35151f2c1bae6bc/digdag-core/src/main/java/io/digdag/core/workflow/WorkflowExecutor.java#L993-L995