Convert hello activities to sync #615

Job	Run time
build-lint-test (3.9, ubuntu-latest)	9s
build-lint-test (3.9, macos-intel)	12s
build-lint-test (3.9, macos-arm)	15s
build-lint-test (3.9, windows-latest)	8s
build-lint-test (3.12, ubuntu-latest)	10s
build-lint-test (3.12, macos-intel)	20s
build-lint-test (3.12, macos-arm)	15s
build-lint-test (3.12, windows-latest)	7s
	1m 36s

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