[FEATURE]: Support AWS_SHARED_CREDENTIALS_FILE for Amazon Bedrock autoload #7924

Feature hasn't been suggested before.

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Describe the enhancement you want to request

I am using Amazon Bedrock to work with OpenCode and I use the AWS_SHARED_CREDENTIALS_FILE with default profile to direct my machine to the AWS credentials.

This feature is missing in the current OpenCode implementation and it only works if I pass the credentials in my env which I would like to avoid.