feat: Allow defining non-error exceptions for control flow

[ditsuke]

Summary

In saq, retry policies and exceptions can be used as a form of control flow. For example, internally, we use a RetryException to indicate that a task should be retried at a later point. However, right now saq will still log the exception as an error which makes for some log noise. Here I propose to introduce a way to pass a set of exception types that saq will not log as errors.