treewide: use get_all_packs

treewide: use get_all_packs

There are many places in the codebase that want to iterate over
all packfiles known to Git. The purposes are wide-ranging, and
those that can take advantage of the multi-pack-index already
do. So, use get_all_packs() instead of get_packed_git() to be
sure we are iterating over all packfiles.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>