macOS installer should remove existing bundles

Would allows:
- downgrade
- uninstalling by not checking anything
I think it can only be done by sh scripting, since the pkgbuild property list will not actually work as documented.

Start by locating the macOS installer and the pkgbuild property list referenced in the issue, then identify where sh scripting could control existing bundles. Done means the installer supports downgrading and removes selected bundles when no components are checked; the issue does not name files or tests to run.

Written by the indexing model from the issue text.