Remove NormalizedNodeOutputStreamWriter

Remove NormalizedNodeOutputStreamWriter

This class is tied to NeonSR2 serialization format through subclassing,
where it really is a package-private detail. This leads to two concrete
classes being in existence for a particular format, which simply does
not make sense.

Eliminating this subclass allows us to make Neon SR2 final, thus arriving
and monomorphic or bimorphic invocation of all methods based on whether
we have seen Lithium (well, Oxygen) format at runtime.

Change-Id: I9e0463ec4879900e82cf757006dccfdbeb0d7297
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>