Function convert_allocation_plan_to_repartition_plan 

pub fn convert_allocation_plan_to_repartition_plan(
    table_id: TableId,
    next_region_number: &mut RegionNumber,
    _: &AllocationPlanEntry,
) -> RepartitionPlanEntry

Converts an allocation plan to a repartition plan.

Converts an AllocationPlanEntry (which contains abstract region allocation intents) into a RepartitionPlanEntry with concrete source and target region descriptors, plus records information on which regions are newly allocated and/or pending deallocation.

Returns

A Result containing the RepartitionPlanEntry describing exactly the source regions, the target regions (including any that need to be newly allocated), and transition mappings.

Notes

• If new regions are needed, their region ids are constructed using table_id and incrementing from next_region_number.
• For each target, associates the correct region descriptor; for new regions, the region id is assigned sequentially.