Merge branch 'ps/object-file-cleanup' into ps/object-store-cleanup

Merge branch 'ps/object-file-cleanup' into ps/object-store-cleanup

* ps/object-file-cleanup:
  object-store: merge "object-store-ll.h" and "object-store.h"
  object-store: remove global array of cached objects
  object: split out functions relating to object store subsystem
  object-file: drop `index_blob_stream()`
  object-file: split up concerns of `HASH_*` flags
  object-file: split out functions relating to object store subsystem
  object-file: move `xmmap()` into "wrapper.c"
  object-file: move `git_open_cloexec()` to "compat/open.c"
  object-file: move `safe_create_leading_directories()` into "path.c"
  object-file: move `mkdir_in_gitdir()` into "path.c"