Update and pin external GH Actions in CI/CD #820

Job	Run time
build (ubuntu-latest, 3.13, 8.1)	7m 24s
build (ubuntu-latest, 3.9, 8.2)	8m 16s
build (ubuntu-latest, 3.9, latest)	20m 18s
build (ubuntu-latest, 3.13, latest)	21m 2s
build (ubuntu-latest, 3.9, 8.1)	7m 13s
build (ubuntu-22.04, 3.7, latest)	20m 22s
build (ubuntu-latest, 3.13, 8.2)	7m 17s
build (ubuntu-22.04, 3.7, 8.1)	7m 17s
build (ubuntu-22.04, 3.7, 8.2)	7m 34s
fossa-scan / Run fossa scan on repository	31s
fossa-scan / Fetch fossa results	1m 6s
	1h 48m 20s

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