builtin/cat-file: convert struct expand_data to use struct object_id

Convert struct cache_entry to use struct object_id by applying the
following semantic patch and the object_id transforms from contrib,
plus the actual change to the struct:

@@
struct expand_data E1;
@@
- E1.sha1
+ E1.oid.hash

@@
struct expand_data *E1;
@@
- E1->sha1
+ E1->oid.hash

@@
struct expand_data E1;
@@
- E1.delta_base_sha1
+ E1.delta_base_oid.hash

@@
struct expand_data *E1;
@@
- E1->delta_base_sha1
+ E1->delta_base_oid.hash

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>