chore: Move StorageObjectStore into test support without changing coverage

[joshtrichards]

• Resolves: #

Summary

This PR relocates StorageObjectStore from production object store code into test support code.

I've been confused by the presence of this class on numerous occasions. It took until today for me to look closer and realize it's 100% a test support class.

Why:

StorageObjectStore is used as a storage-backed test adapter, but currently lives next to production object store implementations. That makes it easy to confuse with a supported production backend.

Changes:

• moved StorageObjectStore into /tests / etc and out of OC\ namespace
• renamed to StorageBackedObjectStore for added clarity
• updated affected tests and references
• kept the same behavior and test usage patterns after relocation

Notes;

• This change is organizational only.
• The tests affected by the move still exercise the same code paths and functionality for all practical purposes:
  • object-store contract behavior is still covered
  • ObjectStoreStorage behavior is still covered
  • PrimaryObjectStoreConfig coverage is preserved, with the same kind of configured class-string usage as before

TODO

• ...

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