[SDK Configs] Add /configs endpoint fetcher with response convertion to Definitions (FF and Configs)#482

EmilianoSanchez wants to merge 3 commits intorefactor-evaluator-to-support-no-targetsplitio/javascript-commons:refactor-evaluator-to-support-no-targetfrom

sdk-configs-handle-configs-dtosplitio/javascript-commons:sdk-configs-handle-configs-dtoCopy head branch name to clipboard