Convert hello activities to sync #643

Job	Run time
build-lint-test (3.9, ubuntu-latest)	5m 21s
build-lint-test (3.9, macos-intel)	5m 33s
build-lint-test (3.9, macos-arm)	5m 18s
build-lint-test (3.9, windows-latest)	5m 47s
build-lint-test (3.12, ubuntu-latest)	5m 18s
build-lint-test (3.12, macos-intel)	6m 7s
build-lint-test (3.12, macos-arm)	5m 7s
build-lint-test (3.12, windows-latest)	6m 4s
	44m 35s

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