apicoverage: Add --minimum-coverage option
apicoverage: Add --minimum-coverage option

This option comes from review[1]:

> It useful future improvement might be a --minimumCoverage=0.5 or
> something, and then at the end of the main function fail if the
> number of apis coverered is less than 50%. Then we can dump this
> into a regression test

[1]: https://github.com/kubernetes/test-infra/pull/5865

jessfraz/test-infra,krzyzacy/test-infra,jlowdermilk/test-infra,lavalamp/test-infra,shyamjvs/test-infra,brahmaroutu/test-infra,brahmaroutu/test-infra,cblecker/test-infra,cjwagner/test-infra,ixdy/kubernetes-test-infra,kargakis/test-infra,mindprince/test-infra,krzyzacy/test-infra,cjwagner/test-infra,abgworrall/test-infra,shyamjvs/test-infra,krzyzacy/test-infra,dims/test-infra,lavalamp/test-infra,fejta/test-infra,abgworrall/test-infra,krzyzacy/test-infra,fejta/test-infra,shyamjvs/test-infra,michelle192837/test-infra,foxish/test-infra,kubernetes/test-infra,monopole/test-infra,michelle192837/test-infra,ixdy/kubernetes-test-infra,cblecker/test-infra,BenTheElder/test-infra,ixdy/kubernetes-test-infra,ixdy/kubernetes-test-infra,cblecker/test-infra,jessfraz/test-infra,jessfraz/test-infra,lavalamp/test-infra,shyamjvs/test-infra,fejta/test-infra,monopole/test-infra,cjwagner/test-infra,kubernetes/test-infra,dims/test-infra,kubernetes/test-infra,BenTheElder/test-infra,BenTheElder/test-infra,pwittrock/test-infra,fejta/test-infra,brahmaroutu/test-infra,jlowdermilk/test-infra,monopole/test-infra,foxish/test-infra,michelle192837/test-infra,mindprince/test-infra,dims/test-infra,cjwagner/test-infra,mindprince/test-infra,jlowdermilk/test-infra,monopole/test-infra,foxish/test-infra,pwittrock/test-infra,kargakis/test-infra,fejta/test-infra,BenTheElder/test-infra,abgworrall/test-infra,BenTheElder/test-infra,foxish/test-infra,kubernetes/test-infra,kargakis/test-infra,shyamjvs/test-infra,michelle192837/test-infra,dims/test-infra,mindprince/test-infra,BenTheElder/test-infra,fejta/test-infra,foxish/test-infra,kubernetes/test-infra,kargakis/test-infra,brahmaroutu/test-infra,kubernetes/test-infra,cjwagner/test-infra,monopole/test-infra,brahmaroutu/test-infra,krzyzacy/test-infra,pwittrock/test-infra,lavalamp/test-infra,cblecker/test-infra,dims/test-infra,lavalamp/test-infra,abgworrall/test-infra,monopole/test-infra,cjwagner/test-infra,michelle192837/test-infra,jessfraz/test-infra,dims/test-infra,pwittrock/test-infra,cblecker/test-infra,krzyzacy/test-infra,brahmaroutu/test-infra,jessfraz/test-infra,jlowdermilk/test-infra,lavalamp/test-infra,jlowdermilk/test-infra,shyamjvs/test-infra,kargakis/test-infra,michelle192837/test-infra,jlowdermilk/test-infra,kargakis/test-infra,abgworrall/test-infra,ixdy/kubernetes-test-infra,cblecker/test-infra,jessfraz/test-infra,mindprince/test-infra,pwittrock/test-infra