Fix the mapping between CWL inputs, which are in JSON format, and Python...

Fix the mapping between CWL inputs, which are in JSON format, and Python types, for CWL steps that contain inline Python script.

The solution is to convert the CWL `$(inputs)` once to a Python `dict`, by using the `json.loads()` function, passing the `$(inputs)` as a raw Python string. Next, any input argument can be accessed as an entry in a Python `dict`.

Also, to avoid potential "Argument list too long" errors, all inline Python scripts that expand the `$(inputs)` argument are now automatically turned into a script *file*, instead of being passed as a (potentially huge) string on the command line.


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Former-commit-id: 2b7fc297