pack-bitmap.c: use `ewah_or_iterator` for type bitmap iterators

pack-bitmap.c: use `ewah_or_iterator` for type bitmap iterators

Now that we have initialized arrays for each bitmap layer's type bitmaps
in the previous commit, adjust existing callers to use them in
preparation for multi-layered bitmaps.

Signed-off-by: Taylor Blau <redacted>
Acked-by: Elijah Newren <redacted>
Signed-off-by: Junio C Hamano <redacted>