464xlat: add ip rule logic in the proto shell handler

Integrate ip rule support for the prelocal routing table lookup in the 464xlat
proto shell handler as netifd does not install anymore an ip rule for the prelocal
routing table.
The prelocal routing table ip rule needs to be installed before the local routing
table ip rule so the 464xlat traffic with as destination the IPv6 anycast address
is routed to the nat46 module otherwise the traffic will be dropped in the IPv6
local table.

Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>