object-file: inline calls to read_object()

object-file: inline calls to read_object()

Since read_object() is these days just a thin wrapper around
oid_object_info_extended(), and since it only has two callers, let's
just inline those calls. This has a few positive outcomes:

  - it's a net reduction in source code lines

  - even though the callers end up with a few extra lines, they're now
    more flexible and can use object_info flags directly. So no more
    need to convert die_if_corrupt between parameter/flag, and we can
    ask for lookup replacement with a flag rather than doing it
    ourselves.

  - there's one fewer function in an already crowded namespace (e.g.,
    the difference between read_object() and read_object_file() was not
    immediately obvious; now we only have one of them).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>