Merged PR 320: #2419- Created a Router-specific version of SessionManager

## Summary
Created a Router-specific version of `SessionManager` that looks at route table rather than default gateway when dst ip address isn't for a locally attached network. Carried these changes through to arp. Added test for this. Made some minor improvements to show functions in container and node that assist debugging.

## Test process
TDD approach: wrote the test, ran it and watched it fail. The implemented the fix and re-ran the test; it passes.

**Before fix:**
![image (2).png](https://dev.azure.com/ma-dev-uk/b50a61ee-86c4-48bc-9a0b-a67645ba12ee/_apis/git/repositories/2825053e-bd3b-45b2-8680-1281809eefa2/pullRequests/320/attachments/image%20%282%29.png)

**After fix:**
![image.png](https://dev.azure.com/ma-dev-uk/b50a61ee-86c4-48bc-9a0b-a67645ba12ee/_apis/git/repositories/2825053e-bd3b-45b2-8680-1281809eefa2/pullRequests/320/attachments/image.png)

## Checklist
- [ ] PR is linked to a **work item**
- [ ] **acceptance criteria** of linked ticket are met
- [ ] performed **self-review** of the code
- [ ] written **tests** for any new functionality added with this PR
- [ ] updated the **documentation** if this PR changes or adds functionality
- [ ] written/updated **design docs** if this PR implements new functionality
- [ ] updated the **change log**
- [ ] ran **pre-commit** checks for code style
- [ ] attended to any **TO-DOs** left in the code

#2419

Related work items: #2419

tests/integration_tests/network/test_routing.py

@@ -152,6 +152,17 @@ def test_with_routes_can_ping(multi_hop_network):
     assert pc_a.ping(pc_b.network_interface[1].ip_address)
 
 
+def test_ping_router_port_multi_hop(multi_hop_network):
+    pc_a = multi_hop_network.get_node_by_hostname("pc_a")
+    router_2 = multi_hop_network.get_node_by_hostname("router_2")
+
+    router_2.route_table.add_route(
+        address="192.168.0.0", subnet_mask="255.255.255.0", next_hop_ip_address="192.168.1.1"
+    )
+
+    assert pc_a.ping(router_2.network_interface[1].ip_address)
+
+
 def test_routing_services(multi_hop_network):
     pc_a = multi_hop_network.get_node_by_hostname("pc_a")