Merge branch 'ps/odb-for-each-object' into seen

Merge branch 'ps/odb-for-each-object' into seen

Revamp object enumeration API around odb.

Comments?

* ps/odb-for-each-object:
  odb: drop unused `for_each_{loose,packed}_object()` functions
  reachable: convert to use `odb_for_each_object()`
  builtin/pack-objects: use `packfile_store_for_each_object()`
  odb: introduce mtime fields for object info requests
  treewide: drop uses of `for_each_{loose,packed}_object()`
  treewide: enumerate promisor objects via `odb_for_each_object()`
  builtin/fsck: refactor to use `odb_for_each_object()`
  odb: introduce `odb_for_each_object()`
  packfile: introduce function to iterate through objects
  packfile: extract function to iterate through objects of a store
  object-file: introduce function to iterate through objects
  object-file: extract function to read object info from path
  odb: fix flags parameter to be unsigned
  odb: rename `FOR_EACH_OBJECT_*` flags