Add -hide-package for installed versions of Home Unit packages

[Saizan]

As a follow up on #284 we were wondering how to stop users from stepping on the footgun of importing a home unit module qualified and getting a previously installed version of it rather than the one their are debugging.

We could prevent this by hiding those installed packages, if we have a good way to find them.

[alt-romes]

We could find by looking up all by package name for all units in the home unit?