Add hybrid plugin system notebook

[feltech]

Add notebook for the design, documentation and e2e testing of the Hybrid Plugin System introduced in https://github.com/OpenAssetIO/OpenAssetIO/issues/1202

Current rendered version

Notebook Driven Development :wink:

• [x] Design API by documentation / example sketches (notebook cannot be executed at this stage)
• [x] Verify locally by executing notebook against proposed upstream changes, making tweaks to the design as necessary.
• [x] Test final released upstream changes against the notebook as part of CI.
• [x] Document by tidying / expanding the notebook to become fully-fledged documentation.

[feltech]

Some minor questions, but if I'm reading the code correctly, the code in these notebooks get run in the CI, so they _have to be correct or the CI will fail?

Yeah exactly. Unfortunately, since we don't publish SimpleCppManager, this notebook only runs in CI on Linux (Docker). I added https://github.com/OpenAssetIO/OpenAssetIO/issues/1408 as a consequence.