View and delete IAM things

[MikaelSmith]

We want to be able to find IAM things based on metadata, and potentially delete them.

Need to explore what precisely are worth exposing. Some candidates: users, groups, roles, policies, entities, instance profiles. https://docs.aws.amazon.com/sdk-for-go/api/service/iam has ways to list a bunch of things, but some of them operate on a particular user/group/etc and should be additional details under those. We don't expect to expose all available information in this first pass.

The outcome should be a new IAM directory in the AWS hierarchy with several types of resources under it: users, groups, roles, policies are a good start. Those should have relevant metadata for searching, and support Delete.