copy: Support both inode exclusion and contents exclusion

copy: Support both inode exclusion and contents exclusion

In some cases, we want to exclude a directory's contents but not
the directory itself. In other cases, we want to exclude a directory
and its contents. Let's extend the denylist logic in copy.h to support
both by changing the denylist from a set to hashmap so we can store the
deny type as the value.

We also modify the repart ExcludeFiles= option to make use of this. If
a directory to exclude ends with a "/", we'll only exclude its contents.
Otherwise, we'll exclude the full directory.