ctor-eval crashes when the same name is imported twice

[stevenfontanella]

#8115 (comment)

Caused by #8115. We should create a stub only once for each qualified name. Also, if a name is imported multiple times with different types, we can try to make a stub with a common subtype that allows both imports to work (e.g. unreachable for functions since stubs can't be called anyway).

[tlively]

Oh interesting, especially the part about importing the same name multiple times. Usually a function cannot have type unreachable, and I wouldn't be surprised if that causes some assertions to fail somewhere, but maybe it would be ok in this special case.