lstree: Move package to localrepo

The lstree package contains a helper for reading a tree. There is no reason why this code needs to be in its own package. In fact, this makes it harder when for instance, we might want to add code in the localrepo package that calls ListEntries() since it would result in a dependency cycle because lstree depends on localrepo.

Move the code under lstree under localrepo, since that is the one stop shop for operations on local repositories.