414913 - WebSocket / Performance - reduce ByteBuffer allocation/copying during generation/writing

+ Splitting Header bytes from payload bytes.
+ returning List<ByteBuffer> from WriteBytesProvider now
+ returning possibly more than 1 frame per
  WriteBytesProvider.getByteBuffers() for submission to
  Endpoint.write()'s gathered write of multiple bytebuffers
WebSocket / Performance - cleaning up tests from fallout on bug 414913

+ Copying payload in test cases for comparison reasons, as the reuse of
  payloads by the implementation now means that the payload might be
  masked by a random client side mask.
+ Cleaning up Abnormal Close handling for idle timeout cases
+ Fixing logging a tag
+ Fixing intermittent test failure in jsr EchoTest