feat: Use CURL multi. #2494

Job	Run time
contract-tests-curl	2m 41s
contract-tests	2m 54s
build-test	5m 39s
build-test-curl	5m 35s
build-test-client-mac	6m 19s
build-test-client-mac-curl	6m 44s
build-test-client-windows	16m 3s
build-test-client-windows-curl	17m 34s
	1h 3m 29s

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