change mutateAsync's name

[schmitch]

currently mutateAsync works differently than mutate in more ways than just "can be awaited".

currently mutateAsync will throw when an error is happening, however mutate will never throw.
basically there is no api for mutate and await till isPending is false without throwing errors.

I think mutateAsync has a ill defined name because of that, it should be more like resultAsync or something and mutateAsync should never throw and always return Promise<void> (success) so that one can await the mutation completly without try/catch.