If the avatar file in storage does not exist, it is not an error and
the database can be updated.
See 1be797faba Fix bug on avatar
(cherry picked from commit d2c4d833f4)
Support to iterator subdirectory in ObjectStorage for
ObjectStorage.Iterator method.
It's required for https://github.com/go-gitea/gitea/pull/22738 to make
artifact files cleanable.
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Co-authored-by: Jason Song <i@wolfogre.com>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>