Refactor mount providers files_sharing app

[salmart-dev]

Summary

This branch contains some changes to clean up the two mount providers of the app:

• applies DRY in some of the most used functions
• removes unnecessary array_values
• splits big functions into multiple smaller functions to ease code navigation

The branch is part of this set of branches:

• master
  • Refactor mount providers files_sharing app #56537 👈
    • Add INodeByPath to Directory #54441
      • Path specific Filesystem setup #55072
        • Implement path-based FS Setup in server MountProviders #56538

TODO

• Consider removing the $validateShares flag, as technically it is a change needed for a child branch and is not a refactoring

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)