Update actions/checkout action to v7 #3467

Job	Run time
Cache identify	5s
Dependency	4s
Shellcheck	6s
Prepare	21s
Ruff check and force	7s
Check commit	31s
Run pytest using Python 3.14	30s
Process test coverage	17s
Run mypy	0s
Build and publish Python 🐍 distributions 📦 to TestPyPI	8s
Process test complexity	10s
	2m 19s

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