[Thread] request/release the NAT64 CIDR

This CL implements the logic to maintain the NAT64 CIDR at ThreadNetworkControllerService. When NAT64 is enabled, the service needs to request a CIDR via RoutingCoordinatorManager#requestDownstreamAddress(). When NAT64 is disabled, the service needs to release the CIDR via RoutingCoordinatorManager#releaseDownstreamAddress().

Bug: 350699020

Change-Id: I16397fd48c2925efd9d4833a335cf73832b4f4d6
5 files changed