EncoderHttpMessageWriter supports streaming MediaTypes

Support for flushing in EncoderHttpMessageWriter is now driven from a
configurable list of "streaming" media types with the list including
"application/stream+json" by default.

As a result Jackson2ServerHttpMessageWriter is no longer needed.

spring-core/src/main/java/org/springframework/core/codec/AbstractEncoder.java

@@ -31,13 +31,6 @@ import org.springframework.util.MimeType;
  */
 public abstract class AbstractEncoder<T> implements Encoder<T> {
 
-	/**
-	 * Hint key to use with a {@link FlushingStrategy} value.
-	 */
-	public static final String FLUSHING_STRATEGY_HINT = AbstractEncoder.class.getName() + ".flushingStrategy";
-
-	public enum FlushingStrategy { AUTO, AFTER_EACH_ELEMENT }
-
 	private final List<MimeType> encodableMimeTypes;