refactor(coreinit): use custom FlagSet
refactor(coreinit): use custom FlagSet

mwitkow/fleet,wuqixuan/fleet,webwlsong/fleet,dongsupark/fleet,bcwaldon/fleet,dalbani/fleet,dalbani/fleet,mwhooker/fleet,giantswarm/fleet,bviswana101/fleet,dongsupark/fleet,mwitkow-io/fleet,paveltiunov/fleet,mischief/fleet,octoblu/fleet,coreos/fleet,esatterwhite/fleet,ecnahc515/fleet,coreos/fleet,bviswana101/fleet,thepwagner/fleet,thepwagner/fleet,jonboulle/fleet,jonboulle/fleet,improbable-io/fleet,WPMedia/fleet,ecnahc515/fleet,mookjp/fleet,mwhooker/fleet,dongsupark/fleet,improbable-io/fleet,mwitkow/fleet,endocode/fleet,endocode/fleet,ecnahc515/fleet,endocode/fleet,improbable-io/fleet,octoblu/fleet,esatterwhite/fleet,WPMedia/fleet,hhoover/fleet,mischief/fleet,bcwaldon/fleet,paveltiunov/fleet,mookjp/fleet,flandr/fleet,dalbani/fleet,webwlsong/fleet,giantswarm/fleet,jonboulle/fleet,giantswarm/fleet,wuqixuan/fleet,hhoover/fleet,coreos/fleet,mwitkow-io/fleet,flandr/fleet,bcwaldon/fleet