feat: lazy load jsonParser and yamlParser FlagFileParser #37

Job	Run time
test-contract-tests	2m 54s
test-platforms-and-versions (ubuntu-20.04, 8)	2m 14s
test-platforms-and-versions (ubuntu-20.04, 11)	2m 20s
test-platforms-and-versions (ubuntu-20.04, 17)	2m 17s
test-platforms-and-versions (ubuntu-20.04, 19)	2m 37s
test-packaging	3m 14s
	15m 36s

Provide feedback