Performance improvements for Nextcloud 24

[ChristophWurst]

Description

Let's analyze our apps and components and improve performance where necessary.

Affected components

• Calendar
• Calendar Resource Management
• Contacts
• Mail

To do

• [x] https://github.com/nextcloud/mail/issues/5835
• [x] https://github.com/nextcloud/server/issues/29563
• [x] https://github.com/nextcloud/groupware/issues/28

To evaluate

• https://github.com/nextcloud/groupware/issues/24