fix(dav): move orphan cleaning logic to a chunked background job

[st3iny]

• Resolves: [Bug]: Upgrade 30.0.10 to 31.04 (dav) requires 6GB of RAM on single-user instance #52505

Summary

It is not required to run the orphan cleanup synchronously during upgrades. I moved it to an async background job to be run some time after the repair jobs ran.

1. Move cleaning up orphaned CalDAV and CardDAV children to an async background job.
2. Chunk it to batches of 1000 to mitigate excessive RAM usage on large instances.

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)

[st3iny]

/backport to stable30

[st3iny]

/backport to stable31

[st3iny]

I rebased and squashed. Nothing else changed.

[backportbot]

The backport to stable31 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable31
git pull origin stable31

# Create the new backport branch
git checkout -b backport/52589/stable31

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick d0fcb7e6

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/52589/stable31

Error: Failed to clone repository: Failed to clone and cache repo: Error: spawn ENOTCONN

---

Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.

[backportbot]

The backport to stable30 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable30
git pull origin stable30

# Create the new backport branch
git checkout -b backport/52589/stable30

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick d0fcb7e6

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/52589/stable30

Error: Failed to clone repository: Failed to clone and cache repo: Error: spawn ENOTCONN

---

Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.

[st3iny]

/backport to stable30

[backportbot]

The backport to stable30 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable30
git pull origin stable30

# Create the new backport branch
git checkout -b backport/52589/stable30

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick d0fcb7e6

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/52589/stable30

Error: Failed to clone repository: Failed to clone and cache repo: Error: spawn ENOTCONN

---

Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.

[st3iny]

/backport to stable31

[st3iny]

/backport to stable30