Create dynamic routes for AS statically configured routing-key

We already do so for routing-keys registered through RKM.
Let's do it too for statically configured ones.

This makes it easier to configure default routing on an STP, since
there's no need to set up "update route" for the most usual cases.
If specific routing is required (eg. combined linkset loadsharing use
over multiple AS on a given PC), it can still be configured manually
using a higher prio in the routing table.

The newly created dynamic routes contain the "match_as_routing_key"
setting, which means they are only usable to route a given message if
its routing label matches the routing-key of the AS.

This opens the door to improved traffic forwarding security as well as
more fine-grained traffic routing selection based on eg. OPC.

So far only matching on DPC and optionaly on OPC is supported.
Matching on SI and SSN is left as TODO work for the future.

Related: OS#7070
Change-Id: Ie74f4b502d4e5beacbf1ac5cd772b8735ea853ed
---
M src/ss7_as.c
M src/ss7_as_vty.c
M src/ss7_combined_linkset.c
M src/ss7_route.c
M src/ss7_route.h
M src/ss7_vty.c
M tests/vty/osmo_stp_route_prio.vty
7 files changed, 76 insertions(+), 21 deletions(-)