tree: Add _create_from_treeinfo() API
osinfo_tree_create_from_treeinfo() API has been added so apps can stick to whatever is their preference on downloading the treeinfo file, mainly now that ftp:// is not supported by _create_from_location(), and just pass the treeinfo file content to libosinfo in order to create an OsinfoTree.
Signed-off-by: Fabiano Fidêncio fidencio@redhat.com