Convert hello activities to sync #618

Job	Run time
build-lint-test (3.9, ubuntu-latest)	1m 1s
build-lint-test (3.9, macos-intel)	1m 8s
build-lint-test (3.9, macos-arm)	1m 0s
build-lint-test (3.9, windows-latest)	58s
build-lint-test (3.12, ubuntu-latest)	1m 8s
build-lint-test (3.12, macos-intel)	1m 9s
build-lint-test (3.12, macos-arm)	52s
build-lint-test (3.12, windows-latest)	59s
	8m 15s

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