Currently the AWS cloud provider uses the EC2 instance role when
interacting with AWS APIs. This change gives the option to provide and IAM
role that the cloud provider will assume before calling the APIs. All
resources created by the role will be owned by that account instead of
the account where the EC2 instance is running.
Means we can run in newly announced regions without a code change.
We don't register the ECR provider in new regions, so we will still need
a code change for now.
This also means we do trust config / instance metadata, and don't reject
incorrectly configured zones.
Fix#35014