Resolve "DIRECTORY only used for uploading backup to remote storage"

What does this MR do?

Add the LOCAL_DIRECTORY environment variable in order to allow grouping backups in local directory too. Verify the existence of the directory and if the rights permissions are set.

EDIT: I wanted to modify the DIRECTORY environment variable to UPLOAD_DIRECTORY environment variable for gitlab:backup:create rake task but to ensure non breaking update for user, I let DIRECTORY.

Are there points in the code the reviewer needs to double check?

Yes, ensure the compatibility with the upload function, it was only tested on a local backup.

Why was this MR needed?

Allow setting a better backup policy, you can now separate local backups into daily, weekly and monthly backup, etc.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered
• End-to-end tests pass (package-qa manual pipeline job)

What are the relevant issue numbers?

Closes #38949 (closed)