Optimize copying workdir tool outputs

We discussed this over ~🍻~ soup last night - right now Galaxy just issues a ``cp`` command for these outputs and doesn't verify the ``cp`` worked. We should try to do a hardlink before copying and we should track whether this cp was successful or not.

Ping @natefoo - this is what we talked about right?

Start by locating the Galaxy code that issues the cp command for workdir tool outputs and read the surrounding output-copy path. Verify how hardlinking can be attempted before copying and how the result of the copy is currently handled; done means both behaviors are implemented and covered by relevant tests.

Written by the indexing model from the issue text.