Update scripts so they will work properly on VFs with multiple axes

I think I've sorted the VF instance name/stat table issue for variable fonts with multiple axes. Once Dave has confirmed he's happy, we can update the scripts in this repo.

Review the scripts in this repository and the variable-font instance name/stat table behavior for fonts with multiple axes. The issue does not name a file or test, and work is contingent on Dave's confirmation; done means the scripts work properly for multi-axis VFs after that confirmation.

Written by the indexing model from the issue text.