fix(core): Add alternative rethrow method by wrapping yield

[kitten]

Related #2191

Summary

Originally, we introduced a check called hasResult, which determined whether we'd rethrow an error, or treat it as a network error.
This check must now be changed to further isolate the non-network errors to the yield operation in our response streams. Specifically, when yielding, the resulting error may come from downstream exchanges, bindings, or the UI framework.

We now detect this differently by wrapping the yield in a boolean flag.

Another thing I've noticed is that Safari doesn't seem to notice broken response streams. While any other browser seems to throw a TypeError, for some reason Safari seems particularly unbothered and simply waits infinitely. It's possible there's a rather long timeout in its fetch logic, but I'll have to test this further as well.

Set of changes

• Replace rethrow check with boolean flag checking whether we're yielding to downstream code