Schedule CRD: add option to specify Timezone

[mmueller-rs]

Describe the problem/challenge you have
In some countries, there are seasonal time changes twice a year.
Depending on the environment and external dependencies, it might be necessary to specify the timezone one is in to be able to set the time for the Schedule based on local time, i.e.:

• Execute a Backup right before working hours
• Execute a backup during noon (when most people are on break)
  That timezone should follow the seasonal time changes.

Describe the solution you'd like
In the CRD for the "Schedule", one should be able to specify the Timezone (similar to how it's done for Kubernetes Cronjobs).

Anything else you would like to add:
[Miscellaneous information that will assist in solving the issue.]