[v2] IAM policy generation wizard

Inspired by this tweet: https://twitter.com/heitor_lessa/status/1361216277407277056 about the [`iam-policies-cli`](https://github.com/mhlabs/iam-policies-cli) tool by @ljacobsson, it would be awesome to expose IAM policy generation as a CLI wizard. Specifically, it would walk you through coming up with a policy by allowing you to select through the various:

* Services
* API operations
* Resource arns

Then as a bonus goal, it would be great if this wizard was also invocable from the `iam wizard new-role` wizard by allowing you to enter this policy generation wizard to create a policy instead of having to select from the preexisiting policies.