Support Terraform to fetch the EC2 metadata and authorize with the identity

[subshree]

Is your feature request related to a problem? Please describe.

This is to support Terraform Extension for Azure DevOps to create AWS resources. We are using self-hosted agents running as EC2 in the account we want Terraform to act in. Is there a way to get Terraform to use the EC2 Instance Metadata of the host EC2 instead of a service connection? -- This is related to an open issue on azure-pipelines-extension

Describe the solution you'd like

Pulling in the comment @hunterwerlla made so we can track it here:

"For the AWS Toolkit for Azure DevOps we support this use case by making the authentication optional. It would make sense to make provider optional/add a noop "Environment" option, so if the machine already has credentials, they can be used."

Describe alternatives you've considered

Additional context