Type Alias OffenceQueueEras

Tracks the eras that contain offences in OffenceQueue, sorted from earliest to latest.

• This ensures efficient retrieval of the oldest offence without iterating through OffenceQueue.
• When a new offence is added to OffenceQueue, its era is inserted in sorted order if not already present.
• When all offences for an era are processed, it is removed from this list.
• The maximum length of this vector is bounded by BondingDuration.

This eliminates the need for expensive iteration and sorting when fetching the next offence to process.