MSI: Add proper uninstallation

[lrandersson]

Checklist

• [x] I added a descriptive title
• [x] I searched open requests and couldn't find a duplicate

What is the idea?

Based on the work in https://github.com/conda/constructor/pull/1084, when you run the uninstaller, not all of the files are removed. In fact, only a couple of files are removed (those that are bundled with the uninstaller), everything created by the separate install script needs to be manually deleted after running the uninstaller. The idea is that the files created by the install script are also automatically removed by the uninstaller.

Why is this needed?

This is needed to have a proper uninstallation step, to reach feature parity with the exe installers.

What should happen?

Same behavior between the exe and the msi installers/uninstallers.

Additional Context

No response