Audio::Samples are a move-only class, they can't be copied.

Using this non-copyable class in a std::vector<std::map<..>> does not
compile in Visual Studio 2017, see e.g.:

https://stackoverflow.com/questions/58700780/vector-of-maps-of-non-copyable-objects-fails-to-compile-in-msvc

Replacing the use of vector with list, which does compile.