circuit_resume_edge_reading_helper checks wrong package window
In order to decide the maximum it can package on a circuit, circuit_resume_edge_reading_helper() checks only the circuits package window, which is not used if layer_hint is non-NULL.
The consequences of this are unclear. It seems that because the max to package is set to the cell highwater size and queue length if it is too large, this should not have much effect in practice. But we should do the correct check here, in any case.
Found while hooking up congestion control code. Fix will be part of that branch, because I actually fixed it while refactoring the choice of which package window to use into a function.