utils: avoid using internal _imp.is_frozen()
imp has been deprecated for a long time, and were removed in Python 3.12 . As a
workaround, we started using the internal _imp. That is ugly and risky.
It seems less risky to get the functionality in some other way. Here, we just
inspect if 'origin' of the '__main__' module is set and 'frozen'. That seems to
work and do the same, and might be better than using the internal _imp
directly.
This way of inspecting module attributes seems to work in some test cases, but
it is a risky change. This level of importlib doesn't have much documentation,
a complicated implementation, and we are dealing with some odd use cases.