Optimizations in the allocator selection: copy the existing state
The random and flq allocators maintain their states. It is particularly long for the FLQ allocator to populate its initial state. It can take from milliseconds to minutes. When a subnet is reconfigured without changing the allocator and the subnet pools, we could perhaps avoid re-building the allocator state but keeping the existing state aside, and then copying the pointer to the allocation state to the new subnet instance. In that case we'd only have the overhead during the startup, renumbering and an allocator change. In all other cases, the reconfiguration would be smooth.