Function upgrade 

pub fn upgrade(
    snapshot: Vec<StateUpdateKind>,
) -> Vec<MigrationAction<StateUpdateKind, StateUpdateKind>>

Adds the additive, behaviorally-inert durable cluster-controller state and reshapes the managed replica location’s availability-zone field:

• ManagedCluster gains auto_scaling_strategy, reconfiguration, and burst, all defaulted to None.
• The managed ReplicaLocation’s single availability_zone user-pin becomes an availability_zones list recording the zones the replica was provisioned under: for a replica of a managed cluster the owning cluster’s current availability_zones (the placement pool); for a replica of an unmanaged cluster its prior single pin, carried across as a zero- or one-element list.

Only the managed Cluster variant and managed ReplicaLocation changed shape, so only those records are rewritten. Unmanaged clusters and unmanaged replica locations are JSON-identical in v87 and are left untouched — emitting an update for them would just retract and re-add the same bytes.