.arcconfig

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.

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