feat: Use CURL multi. #2482

Job	Run time
contract-tests	2m 52s
build-test	5m 30s
build-test-curl	5m 40s
contract-tests-curl	2m 55s
build-test-client-mac-curl	12m 57s
build-test-client-mac	10m 25s
build-test-client-windows-curl	9m 46s
build-test-client-windows	17m 7s
	1h 7m 12s

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