Fix swallowed CancelledError in start_child_workflow and Nexus operations (Issue #1445) #5020

Job	Run time
check-protos	7m 56s
test-latest-deps	9m 46s
features-tests / test	7m 53s
build-lint-test (3.10, ubuntu-arm)	11m 15s
build-lint-test (3.14, ubuntu-arm)	10m 47s
build-lint-test (3.10, windows-latest)	19m 39s
build-lint-test (3.10, macos-intel)	13m 4s
build-lint-test (3.10, macos-arm)	11m 49s
build-lint-test (3.10, ubuntu-latest)	14m 1s
build-lint-test (3.14, windows-latest)	17m 56s
build-lint-test (3.14, macos-intel)	24m 38s
build-lint-test (3.14, macos-arm)	7m 25s
build-lint-test (3.14, ubuntu-latest)	16m 11s
cloud-test	0s
	2h 52m 20s

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