Convert hello activities to sync #604

Job	Run time
build-lint-test (3.9, ubuntu-latest)	17s
build-lint-test (3.9, macos-intel)	23s
build-lint-test (3.9, macos-arm)	20s
build-lint-test (3.9, windows-latest)	15s
build-lint-test (3.12, ubuntu-latest)	17s
build-lint-test (3.12, macos-intel)	34s
build-lint-test (3.12, macos-arm)	22s
build-lint-test (3.12, windows-latest)	15s
	2m 43s

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