ci: Cache Windows boost install #3043

Job	Run time
build-test-client-mac-curl	4m 42s
build-test-curl	6m 10s
build-test-client-windows-curl	12m 31s
build-test-client-windows	12m 25s
contract-tests	3m 37s
contract-tests-curl	3m 34s
build-test-client-mac	3m 15s
build-test	6m 27s
build-test-client-windows	11m 34s
build-test	6m 27s
build-test-client-mac	3m 15s
build-test-client-windows-curl	12m 31s
contract-tests-curl	3m 34s
contract-tests	3m 37s
build-test-curl	6m 10s
build-test-client-mac-curl	4m 42s
	1h 44m 31s

Provide feedback