Add list_pending_activities sample #1097

Job	Run time
build-lint-test (3.10, ubuntu-latest)	11s
build-lint-test (3.14, macos-intel)	14s
build-lint-test (3.14, windows-latest)	13s
build-lint-test (3.14, macos-arm)	30s
build-lint-test (3.10, macos-intel)	15s
build-lint-test (3.10, macos-arm)	20s
build-lint-test (3.10, windows-latest)	18s
build-lint-test (3.14, ubuntu-latest)	28s
	2m 29s

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