Make WDL notice when a file can no longer be used and delete it

[unito-bot]

It would be good if files in WDL workflows were deleted from the job store when they can no longer be accessed by any remaining jobs.

We could add nodes to the workflow graph to delete File values, and make them depend on the completion of all the WDL nodes that actually use those File values, and when they run they delete the files.

I think MiniWDL’s analysis tracks what we would need for this, but we might also want to think about passing sub-environments around the top-level workflow graph that only have the values that actually are referenced, so we don’t feed all the File variables to a bunch of nodes that don’t reference them.

┆Issue is synchronized with this Jira Story
┆Issue Number: TOIL-1540