Fix update-all build profile action

The same disclaimer as before package management applies (i.e. voids
warranty, use at your own risk).
update-{all,packages} build profile action: empty packages dir

... before copying the new contents to the image. This caters to the
typical use case of updating an existing Haiku, making manual
intervention to get the new packages activated unnecessary. The downside
is that manually added packages will be removed as well.
update-{all,packages} build action: Update repository config
Also add repository cache files to image

This makes package management operations that require a repository cache
immediately usable (even offline). Also makes sense for the
update-{all,packages} build profile actions, since those update the
repository config which would otherwise no longer match a potentially
existing cache.
FilterView: Fix depot list.

- Since the package list is built lazily in the background, the list of
  depots won't actually be available immediately at construction time.
  Defer building the menu for both that and the categority list until the
  model has actually been populated.
HaikuDepot: Show packages that don't have a repository.

- If a package was installed, but didn't have a corresponding remote
  repository package, it would have been missed in the list. Detect these
  and create a special local depot object to house them, so they also make
  their way into the visible package list.

Thanks to diver for reporting the discrepancy.