Merged PR 376: 2457 - Remove Hardcoding from Links

## Summary
This PR removes the hardcoding of Link bandwidth, and makes it possible to be configured via the network yaml definitions.
Link bandwidth will still default to 100 if this is not present, to prevent breaking all previous defined networks.

## Test process
All tests continue to pass.
`basic_network_config.yaml` now provides a non-default link bandwidth which is confirmed within unit tests.

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

Related work items: #2457

docs/source/configuration/simulation.rst

@@ -64,10 +64,12 @@ this results in:
         endpoint_a_port: 1 # port 1 on computer_1
         endpoint_b_hostname: switch
         endpoint_b_port: 1 # port 1 on switch
+        bandwidth: 100
         - endpoint_a_hostname: computer_2
         endpoint_a_port: 1 # port 1 on computer_2
         endpoint_b_hostname: switch
         endpoint_b_port: 2 # port 2 on switch
+        bandwidth: 100
 
 ``ref``
 ^^^^^^^
@@ -95,3 +97,7 @@ The ``hostname`` of the node which must be connected.
 
 The port on ``endpoint_b_hostname`` which is to be connected to ``endpoint_a_port``.
 This accepts an integer value e.g. if port 1 is to be connected, the configuration should be ``endpoint_b_port: 1``
+
+``bandwidth``
+
+This is an integer value specifying the allowed bandwidth across the connection. Units are in Mbps.