refactor: use Share for most SharingManager parameters instead of just the id

[icewind1991]

Summary

Change most methods in ISharingManager from taking an string $id to a Share $share, and return the updated share for any relevant methods.

• Prevent unexpected behavior when calling update methods on shares that don't exist
• Since all of those methods ended up fetching the shares anyway for processShareUpdates, having the caller fetch the share (if they don't have it already) is free.
• We no longer need to fetch the owner from the db to perform access checks
• We have the full share data to perform more advanced access checks in the future
• The caller no longer needs to re-fetch the share after modifying it

As part of making this work properly, default values for permissions/properties are now applied once a source/recipient is added instead of only when listing 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