Break out extend_plug_device_class() function #6025

Job	Run time
Shellcheck	5s
Dependency	5s
Cache identify	5s
Prepare	11s
Ruff check and force	8s
Check commit	23s
Run pytest using Python 3.14	21s
Run pytest using Python 3.13	21s
Run mypy	13s
Process test coverage	18s
Build and publish Python 🐍 distributions 📦 to TestPyPI	9s
Process test complexity	9s
	2m 28s

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