Voluntary deregistration

[ppolewicz]

Description

This PR introduces the entire voluntary-deregistration feature set for subnets. We now track subnets that wish to be pruned via a dedicated SubnetDeregistrationPriorityQueue, before using the old immunity/price pruning flow. Subnet owners (or root) can call schedule_deregistration_priority, which creates a timed entry using a configurable DeregistrationPriorityScheduleDelay. Once the (~5 day) delay elapses, the scheduler enqueues the subnet for deregistration, firing SubnetDeregistrationPriorityQueueAdded event, and from this point get_network_to_prune will prefer these queued subnets over price-based candidates—even during immunity.

A new helper module encapsulates the lifecycle: scheduling, enqueueing, canceling, clearing, and forcing entries—while the public extrinsics (schedule_deregistration_priority, cancel_deregistration_priority_schedules, enqueue_subnet_deregistration, clear_deregistration_priority) simply perform origin checks and delegate. Dissolution automatically removes any queue/schedule remnants so newly registered subnets never inherit stale priority. Root can adjust the delay via the new sudo_set_deregistration_priority_schedule_delay and all runtimes/mocks/benchmarks now provide and exercise this constant.

Events were implemented (SubnetDeregistrationPriorityScheduleAdded/Removed, …QueueAdded/Removed, DeregistrationPriorityScheduleDelaySet) to reflect the queue-centric design, and there is a new cradle-to-grave test (schedule_priority_full_lifecycle_to_dissolution) that schedules a subnet for deregistration, simulates the scheduler firing, confirms pruning behavior and dissolves the subnet while asserting each event fires at the right time.

Checklist

• [x] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [x] I have run ./scripts/fix_rust.sh to ensure my code is formatted and linted correctly
• [ ] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [x] Any dependent changes have been merged and published in downstream modules

[JohnReedV]

Looks good. Need to fix CI

[ppolewicz]

I fixed most stuff, but I'm still working on it

[ppolewicz]

This is being shelved, lets reopen it if we want it again and not clutter the queue until now