C# printer: an inner class of a generic class needs the outer type's arguments (Outer<A>.Inner) #142

Problem

A class nested in a generic class, used from outside it, needs the outer class's type arguments in C#: Java's
ElementAwareArrayList<Mapped_>.Entry is C#'s ElementAwareArrayList<Mapped_>.Entry. The CST's ParameterizedType
of Entry does not carry the outer type's arguments, so the C# printer writes ElementAwareArrayList.Entry, which
names the non-generic companion class of the static members, where there is no Entry (CS0426).

In timefold this is 5 errors (AbstractToListSlot, AbstractToCollectionSlot, AbstractLeftDatasetInstance,
RandomAccessLeafIndexer). A smaller sample:

public class Holder {
    static final class Store<T> {
        final class Entry { }
        Entry add(T value) { return new Entry(); }
    }
    private Store<String>.Entry cached;
    void keep(Store<String> store) { cached = store.add("x"); }
}

prints private Holder.Store.Entry cached; (wanted: Holder.Store<string>.Entry), and also qualifies Entry
inside Store<T> itself as Holder.Store.Entry, where plain Entry (or Store<T>.Entry) would do.

What is needed

• front end: the outer type's arguments on the ParameterizedType of an inner class's use (javac has them on the
  ClassType's enclosing type);
• C# printer: print them, Outer<A>.Inner, and inside the generic class leave a nested type simple.

Part of #115.