Stop exposing InternalMetadata via the persistence SPI

interface MarshallableEntry<K, V> {
   ByteBuffer getKeyBytes();

   ByteBuffer getValueBytes();

   K getKey();

   V getValue();

   Metadata metadata();

   ByteBuffer metadataBytes();

   long created();

   long lastUsed();

   boolean isExpired(long now);

   long expiryTime();
}

ByteBuffer getMetadataBytes();
InternalMetadata getMetadata();