Draft: Allow for bus vectors to be expanded if they end with a differential pair signifier (+/-, _P/_N)

Hey all,

When working on a design with a large bus off differential pairs, it was noticed that bus vectors with a suffix would fail to expand, making things like a bus with 32 differential pairs painful to define.

This PR is mainly to gauge the idea, and see what the devs think about this. I will 100% admit that it's just a quick hack at the moment, but all the QA tests pass (at least locally, the gitlab piplines are still running as I write this).

It currently just allows for the differential pair suffixes +/-/_P/_N, rather than just any arbitrary string, personally I don't think suffixed vector expansion not being able to auto-increment is not too bad of a thing to have happen.

Either way, I look forward to what people have to say~

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