[WIP] allow every with direct access to a shared file to modify all shares for the file

[icewind1991]

Summary

Allow all users that have direct (not through a share) access, and share permissions to a file access to see and modify all shares for that file, even ones created by other users.

This mirrors the existing logic around IShareOwnerlessMount, but makes the behavior work automatically instead of mounts having to opt-in. Afaik this is equivilent since all mounts I'm aware of that this behavior would trigger for (external storage, groupfolders) opt-in to IShareOwnerlessMount.

We can still change this behavior to require the opt-in from mounts if needed.

• Return shares owned by others when listing shares for a specific file
• Allow modifications to the returned shares

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)

AI (if applicable)

• The content of this PR was partly or fully generated using AI