4d2c2509f2
multipath control plane changed described in D24141. Currently route.c contains core routing init/teardown functions, route table manipulation functions and various helper functions, resulting in >2KLOC file in total. This change moves most of the route table manipulation parts to a dedicated file, simplifying planned multipath changes and making route.c more manageable. Differential Revision: https://reviews.freebsd.org/D24870