builtin-remote: fix two inconsistencies in the output of "show <remote>"

builtin-remote: fix two inconsistencies in the output of "show <remote>"

Remote and stale branches are emitted in alphabetical order, but new and
tracked branches are not. So sort the latter to be consistent with the
former. This also lets us use more efficient string_list_has_string()
instead of unsorted_string_list_has_string().

"show <remote>" prunes symrefs, but "show <remote> -n" does not. Fix the
latter to match the former.

Signed-off-by: Jay Soffian <jaysoffian@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>