add utility command for object store objects

[icewind1991]

Adds some basic utility command for working directly with objects on the object store.

While admins should usually go through the regular file utilities instead of touching the object store directly. In some cases, such as if there is a desync between the object store and filecache, this isn't an option.
If we detect that the admin is trying to touch an object that belongs to an existing file, a warning is shown.

By having an option to do this directly trough occ it removes the requirement for admins to install 3rdparty tools such as s3cmd and the object store configuration can be infered from the nextcloud config.

[artonge]

Some copy-pasting errors, but fine 👍

[icewind1991]

/backport to stable27

[icewind1991]

/backport to stable26

[backportbot-nextcloud]

The backport to stable26 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable26
git pull origin stable26
# Create the new backport branch
git checkout -b fix/foo-stable26
# Cherry pick the change from the commit sha1 of the change against the default branch# This might cause conflicts. Resolve them.
git cherry-pick abc123
# Push the cherry pick commit to the remote repository and open a pull request
git push origin fix/foo-stable26

More info at https://docs.nextcloud.com/server/latest/developer_manual/getting_started/development_process.html#manual-backport