fetchTimeout cannot be disabled in retry middleware

[alex-statsig]

I think there should be a setting to omit the fetchTimeout handling for retry middleware, only retrying for specified statuscodes instead. Reading some code it seemed like there was a case for handling a fetchTimeout value of 0 here to skip the fetch timeout logic entirely. However, providing a fetchTimeout: 0 actually gets overridden here by the || 15000 (rather than ?? 15000).

I can set this value arbitrarily high to avoid the timeout still, but it feels like there should be a more direct way to do that (avoiding the extra setTimeout, and just being cleaner). I think supporting a fetchTimeout value of 0 would be reasonable to handle this? If so, I can contribute a change for it