## Summary
*Replace this text with an explanation of what the changes are and how you implemented them. Can this impact any other parts of the codebase that we should keep in mind?*
## Test process
*How have you tested this (if applicable)?*
## Checklist
- [X] 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
Related work items: #2913
## Summary
* Changed the office LAN convenience function to a class with a registry. Now, plugin can register custom node adders.
* Added ability to define `node_sets` in the config that map to `NetworkNodeAdder` subclasses
* Made airspacefrequency into a DTO class again to make management simpler.
* Moved the node registry out of `HostNode` and `NetworkNode` into `Node`
* Changed game.py to check the hardcoded node types before the node registry (this will change once I add ConfigSchema to all node subclasses)
* Made `show` method of the network container show all nodes, including ones registered at runtime.
## Test process
* Existing tests passed.
* Added unit tests for node adders
## 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
- [X] updated the **change log**
- [X] ran **pre-commit** checks for code style
- [ ] attended to any **TO-DOs** left in the code
