[feat] Support VPCs without NAT Gateways

[jplock]

Related to aws/aws-nitro-enclaves-acm#130

This is blocked until a new release of aws-nitro-enclaves-acm is released that includes this change and available through the AL2023 RPM repositories.

The issue is the current code (v1.3.0) calls the IAM GetRole to https://iam.amazonaws.com which is not available through a VPC endpoint.

[jplock]

https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_interface_vpc_endpoints.html