Convert hello activities to sync #676

Job	Run time
build-lint-test (3.9, ubuntu-latest)	5m 16s
build-lint-test (3.9, macos-intel)	7m 20s
build-lint-test (3.9, macos-arm)	6m 48s
build-lint-test (3.9, windows-latest)	6m 0s
build-lint-test (3.12, ubuntu-latest)	5m 24s
build-lint-test (3.12, macos-intel)	6m 13s
build-lint-test (3.12, macos-arm)	5m 37s
build-lint-test (3.12, windows-latest)	5m 54s
	48m 32s

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