yang: Introduce ietf-routing module with dependencies

We are also going to implement a model dealing with network routing
tables. Such model (ietf-routing) is published in in RFC 8349 [1].
It needs to be augmented for ipv4/ipv6 routing. All the models are
downloaded from YangModels GitHub repository [2] (commit
8dd16482bb74c6add0b187a0e7755f5549da1ccb).

Also note that ietf-routing (as well as ietf-interfaces) also model
*-state containers which are supposed to be `config false;`. We are
actually using config false too but on the configuration containers.
This is done via augmentation in czechlight-network model.

This, however, led to unpleasant situation where I have not realized
that ietf-routing:routing-state depends on
ietf-interfaces:interface-state and the model could not be installed
into sysrepo (see https://github.com/sysrepo/sysrepo/issues/2384).
The augmentation in czechlight-network model had to be altered as well.

[1] https://tools.ietf.org/html/rfc8349
[2] https://github.com/YangModels/yang/tree/8dd16482bb74c6add0b187a0e7755f5549da1ccb/standard/ietf/RFC

Change-Id: I7b7d51b5c67e34acb3fa05c3745335b0ee4957d0
diff --git a/CMakeLists.txt b/CMakeLists.txt
index f2786a6..56692fb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -65,6 +65,9 @@
     yang/czechlight-network@2021-02-22.yang
     yang/iana-if-type@2017-01-19.yang
     yang/ietf-ip@2018-02-22.yang
+    yang/ietf-routing@2018-03-13.yang
+    yang/ietf-ipv4-unicast-routing@2018-03-13.yang
+    yang/ietf-ipv6-unicast-routing@2018-03-13.yang
     )
 
 # Targets
@@ -419,6 +422,9 @@
             YANG ${CMAKE_CURRENT_SOURCE_DIR}/yang/iana-if-type@2017-01-19.yang
             YANG ${CMAKE_CURRENT_SOURCE_DIR}/yang/ietf-interfaces@2018-02-20.yang
             YANG ${CMAKE_CURRENT_SOURCE_DIR}/yang/ietf-ip@2018-02-22.yang
+            YANG ${CMAKE_CURRENT_SOURCE_DIR}/yang/ietf-routing@2018-03-13.yang
+            YANG ${CMAKE_CURRENT_SOURCE_DIR}/yang/ietf-ipv4-unicast-routing@2018-03-13.yang
+            YANG ${CMAKE_CURRENT_SOURCE_DIR}/yang/ietf-ipv6-unicast-routing@2018-03-13.yang
             YANG ${CMAKE_CURRENT_SOURCE_DIR}/yang/czechlight-network@2021-02-22.yang)
     velia_test(sysrepo_system-ietfinterfaces velia-system)
     set_tests_properties(