We don't load casks and formulae that used to exist in an external
tap but have been moved and renamed to an API tap when using the
API. Loading works correctly when the core formula or cask tap
is tapped locally though.

This PR adds some logic to map tap migration renames to the API
and check that when loading formulae and casks.

Check for the following:
- Tap migration rename to core tap can be loaded by short name
- Tap migration rename to core tap can be loaded by long name
- Tap migration renam that clashes with existing core tap short name
  is ignored in favor of loading the cask/formula from the core tap

This changes slightly how we load packaged migrated to core taps
when they are loaded using the API. Now it should show the warning
that the package has been migrated and renamed.