Support new AWS SSO sessions config

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#### Description

The AWS sdk supports a newer way to authenticate with SSO. The new method configures both a profile and a sso-session in ~/.aws/config. See here for more details: https://docs.aws.amazon.com/cli/latest/userguide/sso-configure-profile-token.html

When trying to run Packer with the newer SSO config, I receive the following error:
```
==> build.docker: Error fetching ECR credentials: no valid credential sources for found.
==> build.docker:
==> build.docker: Please see
==> build.docker: for more information about providing credentials.
==> build.docker:
==> build.docker: Error: SSOProviderInvalidToken: the SSO session has expired or is invalid
```

#### Use Case(s)

Using the newer aws sdk.