feat(files): warn when file would be hidden

[susnux]

• Resolves: Warn users when changing format or renaming into hidden file #48533

Summary

1. Add a warning dialog when a file would be hidden (prefixed with a .). Only visible if hidden files are not shown.
2. Fix handling when renaming: If the name is already used by a hidden file this should be forbidden.

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)

[AndyScherzinger]

/backport! to stable33