Unnecessarily performed tasks of kresd instances
By default some tasks are unnecessarily performed on all running kresd instances. This means tasks that only need to be performed once.
- cache prefilling: It only needs to be performed once. Prefilling can also take a relatively long time(#417). Maybe it should be done by some separate process.
- secret for TLS session resumption: By default, each instance has/generates its own secret. Therefore, the clients session tickets for a particular kresd instance are not compatible with other instances. The secret should be the same for all instances and should change automatically at intervals. This ensures compatibility between kresd instances and increases security.