Added FOCUS-60380 - Force the AWS Secrets Manager SDK to use the EC2 Instance Profile Provider

Improves AWS Secrets Manager authentication reliability on EC2-hosted installations by ensuring the application always uses the IAM credentials associated with the server instance when explicit AWS credentials have not been configured. This resolves authentication failures that could occur during site updates and general application use when the previous credential resolution behavior picked up unintended credentials. Sites with explicitly configured AWS credentials are unaffected.