The implementation of __Pyx__PyNumber_Float() wasn't checking whether
errors occurred on the calls to __Pyx_PyUnicode_AsDouble(),
__Pyx_PyBites_AsDouble(), and __Pyx_PyByteArray_AsDouble(). Errors from
those functions were now properly propagated to the caller.

Closes https://github.com/cython/cython/issues/4143