* Make lookup path of `fib<4|6>_lookup_debugnet()` separate functions (`fib<46>_lookup_rt()`). These will be used in the control plane code requiring unlocked radix operations and actual prefix pointer.
* Make lookup part of `fib<4|6>_check_urpf()` separate function. This will be used after algorithmic lookups introduction, by simplifying the switch to alternative lookup implementations.
* While here, use static initializers for IPv4/IPv6 keys