Default nonempty list initializers to Python lists, because the idiom is...

Default nonempty list initializers to Python lists, because the idiom is widely used in lieu of a tuple, and almost never as an actual initialized list that is about to be added even more elements. This removes the possibility to create an initialized tensor list, and to cover for that this CL also introduces a special function for that purpose.

PiperOrigin-RevId: 205771027