Convert hello activities to sync #616

Job	Run time
build-lint-test (3.9, ubuntu-latest)	1m 2s
build-lint-test (3.9, macos-intel)	1m 14s
build-lint-test (3.9, macos-arm)	1m 11s
build-lint-test (3.9, windows-latest)	1m 2s
build-lint-test (3.12, ubuntu-latest)	1m 4s
build-lint-test (3.12, macos-intel)	1m 12s
build-lint-test (3.12, macos-arm)	1m 6s
build-lint-test (3.12, windows-latest)	1m 10s
	9m 1s

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