wq executor: map result filename to parsl task id (#1672)
wq executor: map result filename to parsl task id (#1672)

Towards a solution to #1228.

The process that submits/waits for wq tasks now explicitely remembers
the name of the result file. Before this name was recomputed, making it
very fragile to changes to how files are named.

Co-authored-by: Ben Clifford <6e9c823d93e7dad5e7e2198704c60762764c20c1@hawaga.org.uk>
Parsl/parsl,Parsl/parsl,Parsl/parsl,Parsl/parsl