Previously if you did configure your AWS credentials properly in the EKS
integration, you see an opaque error:

```
Error: Request failed with status code 422
```

This change now provides more direct feedback to the user, such as:

Validation errors:

```
Validation failed: Role arn must be a valid Amazon Resource Name
```

Access denied errors:

```
Access denied: User: arn:aws:iam::123456789012:user/stanhu is not
authorized to perform: sts:AssumeRole on resource:
arn:aws:iam::123456789012:role/stanhu-eks-role
```

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/291016