ART-2892 Find builds rhcos

[thegreyd]

https://issues.redhat.com/browse/ART-2892

Summary

• rhcos x86_64 package - https://brewweb.engineering.redhat.com/brew/packageinfo?packageID=80343 (similar for other arches)
• filemeta API - https://errata.devel.redhat.com/developer-guide/api-http-api.html#advisories
• filemeta discussion on slack
• filemeta view - https://errata.devel.redhat.com/brew/edit_file_meta/118080

Test

• elliott --group openshift-4.13 --assembly 4.13.7 find-builds -k rhcos --use-default-advisory image
• https://errata.devel.redhat.com/advisory/118080

[thegreyd]

Closing in favor of https://github.com/openshift-eng/art-tools/pull/56