Clean stale local storages from `oc_storages` and `oc_filecache`

Description

First of all, sorry if this is a duplicate issue. I did find occurrences of this question on forums (with no convincing answer), but no issue here.

Some time ago, I changed the datadirectory setting of a Nextcloud server (25.x at the time) after manually moving the data to its new path. I did so without taking precautions, and ended up with a new local entry in the oc_storages table:

nextcloud=> SELECT * FROM oc_storages WHERE id LIKE 'local%' ;
 numeric_id |                  id                  | available | last_checked 
------------+--------------------------------------+-----------+--------------
          1 | local::/var/www/html/nextcloud/data/ |         1 |             
        272 | local::/data/nextcloud/data/         |         1 |             

Rescanning the files (occ files:scan --all) made most things work again, and I did not overly bother with the issue after this, but I still have some leftover issues from this: for instance, sub-shares from group folders that must be re-shared, and the previous shares being empty directories (since they still point to the old storage path in the database).

I have since upgraded my instance to 27.1.6, and I would prefer being rid of these stale entries in my database to avoid any future issues. After manually running a files:cleanup (and files:repair-tree, in case it would help), the stale row in the database still has available to 1. I still have many (thousands) entries in oc_filecache with storage id 1, with (as expected) plenty of those duplicated in storage 272 (ie. same path and path_hash), which are not cleaned up as stale.

Steps to reproduce

1. Populate Nextcloud with some files, so that the local:: storage has entries;
2. move the data directory location and change the data path in the configuration file accordingly;
3. rescan files (occ files:scan --all);
4. cleanup file cache (occ files:cleanup)

Expected behavior

The stale entry from oc_storage should disappear, as the files are no longer available at this location (the directory was moved). The stale entries from oc_filecache should be cleaned up accordingly.

Start by tracing the behavior of the mentioned occ files:scan, files:cleanup, and files:repair-tree commands around the oc_storages and oc_filecache tables. Reproduce the moved-datadirectory scenario and verify that stale storage rows and their file-cache entries are removed without affecting the active storage.