Calendar optimizations

[icewind1991]

• preload shares for calendars when listing calendars
• cache calendar objects when doing calendarQuery

These save N queries when listing calendars and when listing calendar objects respectively.

[tcitworld]

This looks really nice.

[kesselb]

Good change 👍

[icewind1991]

/backport to stable27

[icewind1991]

/backport to stable26

[backportbot-nextcloud]

The backport to stable26 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable26
git pull origin stable26
# Create the new backport branch
git checkout -b fix/foo-stable26
# Cherry pick the change from the commit sha1 of the change against the default branch# This might cause conflicts. Resolve them.
git cherry-pick abc123
# Push the cherry pick commit to the remote repository and open a pull request
git push origin fix/foo-stable26

More info at https://docs.nextcloud.com/server/latest/developer_manual/getting_started/development_process.html#manual-backport

[icewind1991]

26: #39861