Convert hello activities to sync #605

Job	Run time
build-lint-test (3.9, ubuntu-latest)	20s
build-lint-test (3.9, macos-intel)	24s
build-lint-test (3.9, macos-arm)	19s
build-lint-test (3.9, windows-latest)	14s
build-lint-test (3.12, ubuntu-latest)	16s
build-lint-test (3.12, macos-intel)	24s
build-lint-test (3.12, macos-arm)	23s
build-lint-test (3.12, windows-latest)	16s
	2m 36s

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