feat: Use CURL multi. #1497

Job	Run time
contract-tests-curl	3m 34s
contract-tests	3m 34s
build-test-server	6m 23s
build-test-server-windows	18m 31s
build-test-server-curl	6m 46s
build-test-server-windows-curl	9m 50s
build-test-server-mac-curl	13m 30s
build-test-server-mac	9m 36s
	1h 11m 44s

Provide feedback