[RFC] Add support for AWS Standard Credential Provider Chain

[AdamTylerLynch]

Recommend implementing the standard credential provider chain as per AWS SDK standards. The providers have an order of precedence, and support refresh tokens for federation, operating in containers, and EC2 assume role.

Adding these would provide consistent experiences across runtime environment, and provide the ability to leverage AWS-lite for specific parts of an application (strangler pattern) without having to change/amend the application’s credential provider.

https://docs.aws.amazon.com/sdkref/latest/guide/standardized-credentials.html