Move the `objects` method to `LfsHelper` so that it is also available to `LfsStorageController`
## What does this MR do?
Move the `objects` method to `LfsHelper` so that it is also available to `LfsStorageController`
It is needed for the `lfs_check_access!` callback when the repository size limit is enabled (EE only).
cc @stanhu @ahanselka
## Why was this MR needed?
Errors shown here: gitlab-org/gitlab-ce#24392
Discovered thanks to gitlab-com/infrastructure#302
## What are the relevant issue numbers?
Fixes#24392Fixesgitlab-com/support-forum#1280
See merge request !7417