Convert hello activities to sync (#173) #691

Job	Run time
build-lint-test (3.9, ubuntu-latest)	5m 18s
build-lint-test (3.9, macos-intel)	7m 55s
build-lint-test (3.9, macos-arm)	9m 0s
build-lint-test (3.9, windows-latest)	5m 56s
build-lint-test (3.12, ubuntu-latest)	5m 18s
build-lint-test (3.12, macos-intel)	6m 9s
build-lint-test (3.12, macos-arm)	5m 27s
build-lint-test (3.12, windows-latest)	6m 5s
	51m 8s

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