ic: add support for routing tables in adv/learn routes

Previously support for multiple routing tables was added
to northd code.
This commit expands support for multiple routing tables
by adding support of advertising and learning routes with
their routing table information.

To utilize such feature, user must:
1. create Logical Router in each AZ;
2. create IC transit switch for each routing table, that
   he/she needs;
3. connect each TS with this LR;
4. assign routing table for TS's LRP
   (ovn-nbctl lrp-set-options <lrp> route_table=<>);
5. enable routes sync (turn on learning and advertising
   routes in NB_Global table);
6. create LRPs for subnets in LR, create static routes
   with supplying route_table parameter.

Note 1: routes for connected networks will be learned to
<main> routing table and if Logical Routers have more than
one Transit Switch, which interconnects them, connected
routes will be added via each transit switch port and
configured as ECMP routes.

Note 2: static routes within route tables will be advertised
and learned only if interconnecting transit switch's LRPs
have same value in options:route_table as NB:Logical_Router_Static_Route
or ICSB:Route route_table column value.

Signed-off-by: Vladislav Odintsov <odivlad@gmail.com>
Reviewed-by: Numan Siddique <numans@ovn.org>
Signed-off-by: Numan Siddique <numans@ovn.org>

NEWS

@@ -24,6 +24,10 @@ OVN v21.09.0 - 01 Oct 2021
   - Allow static routes without nexthops.
   - Enabled logical dp groups as a default.  CMS should disable it if not
     desired.
+  - Added support for multiple routing tables in Logical Router Static Routes
+    and LRPs. OVN Interconnection supports routes' route tables as well.
+    This requires to update schemas for OVN_Northdbound and OVN_IC_Southbound
+    DBs.
 
 OVN v21.06.0 - 18 Jun 2021
 -------------------------