Retries via util-retry vs middleware-retry

[kevindente]

It appears that there are two different retry strategy implementations in the AWS client - @smithy/util-retry and @smithy/middleware-retry. As far as I can tell today, the code is using middleware-retry, and we've implemented a custom retryDecider. However, middleware retry strategy classes appear to be marked as deprecated. Is the codebase migrating over to util-retry? It seems to have WAY less customizability than middleware-retry, and there isn't a way for us to implement what we have today with that library.