Transition from rtrequest1_fib() to rib_action().
Remove all variations of rtrequest <rtrequest1_fib, rtrequest_fib,
in6_rtrequest, rtrequest_fib> and their uses and switch to
to rib_action(). This is part of the new routing KPI.
Submitted by: Neel Chauhan <neel AT neelc DOT org>
Differential Revision: https://reviews.freebsd.org/D25546