Duplicate exported functions in System.Process: callProcessWithOutput and callProcessAndCollectOutput

There are currently two functions exported in System.Process which have the same effect, callProcessWithOutput and callProcessAndCollectOutput. This is a result of the merger of clean-nc and clean which both had their own implementation.

Personally I prefer to export a single function named callProcessAndCollectOutput as I think this name is more descriptive of what the function does.

I would personally prefer the type of callProcessWithOutput as the result is a record type which in my opinion is more descriptive than the triple returned by callProcessAndCollectOutput.

I think the implementation of callProcessWithOutput is simpler as a result of using waitForProcess.

The proposed changes would lead to a major upgrade for platform.

@camilstaps What are your thoughts on this?