notes: convert internal structures to struct object_id

notes: convert internal structures to struct object_id

Convert the internal structures using unsigned char [20] to take
struct object_id using the following semantic patch and the standard
object_id transforms:

@@
struct leaf_node E1;
@@
- E1.key_sha1
+ E1.key_oid.hash

@@
struct leaf_node *E1;
@@
- E1->key_sha1
+ E1->key_oid.hash

@@
struct leaf_node E1;
@@
- E1.key_sha1
+ E1.key_oid.hash

@@
struct leaf_node *E1;
@@
- E1->key_sha1
+ E1->key_oid.hash

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

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

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