added a check if the config initialized with anon creds

[RanVaknin]

For changes to files under the /model/ folder, and manual edits to autogenerated code (e.g. /service/s3/api.go) please create an Issue instead of a PR for those type of changes.

If there is an existing bug or feature this PR is answers please reference it here. https://github.com/aws/aws-sdk-go-v2/issues/1797

Description of changes: When config is created with aws.AnonymousCredentials the provider is being wrapped in a cache and not propagated to the client correctly.

This fix simply checks whether the config is initialized with anonymous creds, and if so, it doesn't wrap them in a cache.