Refactor: libpe_status,libpacemaker: shuffle some node-related functions around

node_list_dup() and node_hash_dup() were declared in libpe_status's internal.h,
but node_hash_dup() was defined in libpacemaker, and neither needed to be in
libpe_status. Move both to libpacemaker, rename to current guidelines, and
declare in libpacemaker's pcmk_sched_utils.h.

Also make the hash table copier more efficient by eliminating an intermediate
conversion to a list.