refactor: Implement cancellation for Delay() timers. #1809

Job	Run time
build-test-server	7m 45s
contract-tests	4m 19s
build-test-server-mac	5m 52s
contract-tests-curl	4m 44s
build-test-server-windows	20m 13s
build-test-server-curl	7m 56s
build-test-server-windows-curl	18m 49s
build-test-server-mac-curl	6m 8s
	1h 15m 46s

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