[POC] use WIX CPack generator for Windows installer

[Be-ing]

This is a quick hack proof of concept to test if we can build smaller installers with WIX than Innosetup. I don't know why Audacity was using Innosetup when CPack can take care of this.

Checklist

• I have signed off my commits using -s or Signed-off-by* (See: Contributing § DCO)
• [N/A] I made sure the code compiles on my machine
• I made sure there are no unnecessary changes in the code*
• I made sure the title of the PR reflects the core meaning of the issue you are solving*
• I made sure the commit message(s) contain a description and answer the question "Why do those changes fix that particular issue?" or "Why are those changes really necessary as improvements?"*

* indicates required