feat: Use CURL multi. #1499

Job	Run time
build-test-server	6m 18s
contract-tests-curl	3m 28s
contract-tests	3m 20s
build-test-server-curl	7m 7s
build-test-server-mac	16m 12s
build-test-server-windows	18m 25s
build-test-server-windows-curl	10m 9s
build-test-server-mac-curl	10m 22s
	1h 15m 21s

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