streaming: move into object database subsystem

The "streaming" terminology is somewhat generic, so it may not be
immediately obvious that "streaming.{c,h}" is specific to the object
database. Rectify this by moving it into the "odb/" directory so that it
can be immediately attributed to the object subsystem.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

meson.build

@@ -397,6 +397,7 @@ libgit_sources = [
   'object-name.c',
   'object.c',
   'odb.c',
+  'odb/streaming.c',
   'oid-array.c',
   'oidmap.c',
   'oidset.c',
@@ -490,7 +491,6 @@ libgit_sources = [
   'stable-qsort.c',
   'statinfo.c',
   'strbuf.c',
-  'streaming.c',
   'string-list.c',
   'strmap.c',
   'strvec.c',