Add String to File functionality into toil-wdl-runner (#4589)

* monkeypatch coerce for workflow related nodes

* Fix task inputs string coerce

* Disable kubernetes

* Comment out cwl kubernetes

* Maybe markers are wrong and comment out cactus-on-kubernetes

* Add docstrings to changed functions + change input list to dict

* Deal with nonetype

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Co-authored-by: Adam Novak <[email protected]>