Request: incorporate newest MegaApiClient library with retry-delay

As @ts678 pointed out, the MegaApiClient library was recently modified to support full customization of the retry delay.

If the development team isn’t already all over this, I’m requesting the new library be incorporated with Duplicati and any new capabilities utilized. I’m not sure whether this library change correlates exactly with what the Duplicati core “retry-delay” option intends. If it does, that would obviously be a simple way to integrate it. If not, I suppose it would have to be a new option.

Whether or not this would help resolve the occasional strange behaviors seen when using as a Duplicati destination, only time will tell.