feat(timed-events): add cron based timed events

[Yoronex]

Description

Replaces the old hardcoded cron jobs with a new cron based timed events system. Using a cron expression, certain types of events can now be scheduled dynamically using CRUD endpoints. The cron-manager keeps track of these cron jobs. Optionally, a timed event can be skipped once (for example, when Hubble is by exception extending its opening times).

Currently, admins can schedule the following types of events:

• Resetting Aurora to its initial state.
• Removing expired audit logs.
• Changing an audio's handler.
• Changing a lights group's handler.
• Changing a screen's handler.

Related issues/external references

Types of changes

• New feature (non-breaking change which adds functionality)