builtin/cat-file: filter objects via object database

builtin/cat-file: filter objects via object database

When batching all objects, git-cat-file(1) reaches into the internals of
the object database and manually manages bitmaps to apply object
filters. This creates coupling between the command and the internals of
the respective backend.

Refactor git-cat-file(1) to use the new object filter option when
batching all objects. This significantly simplifies the logic and
ensures that we don't have to reach into internals of the "files" source
anymore.

Signed-off-by: Patrick Steinhardt <redacted>
Signed-off-by: Junio C Hamano <redacted>