Set log level with custom RetryableStrategy

[avandecreme]

Motivations

If using a custom RetryableStrategy, it does not seem possible to set the retry_log_level because with_retry_log_level is implemented on RetryTransientMiddleware<T, DefaultRetryableStrategy> but not on RetryTransientMiddleware<T, R>

Solution

It seems like the with_retry_log_level function could just be moved from RetryTransientMiddleware<T, DefaultRetryableStrategy> to RetryTransientMiddleware<T, R> (I didn't try, maybe I am missing something).