feat: Use CURL multi. #2480

Job	Run time
contract-tests-curl	2m 41s
contract-tests	2m 45s
build-test	6m 25s
build-test-curl	5m 53s
build-test-client-mac	12m 7s
build-test-client-mac-curl	9m 13s
build-test-client-windows-curl	8m 14s
build-test-client-windows	16m 40s
	1h 3m 58s

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