[cxx-interop] Import iterator types that are not typedef-ed
This prevented `std::vector<std::string>` from being auto-conformed to `CxxRandomAccessCollection`.
If an iterator type is templated, and does not have an explicit instantiation via a typedef or a using-decl, its specialization will not have an owning Clang module. Make sure we treat it as a part of the Clang module that owns the template decl.
rdar://112762768 / resolves https://github.com/apple/swift/issues/67410
