Replace AppendableByteArrayInputStream in DirectDruidClient

* Replace with SequenceInputStream fueled by an enumeration of ChannelBufferInputStream which directly wrap the response context ChannelBuffer


I was seeing a lot of issues with the micro-byte[ ] allocations. This PR is an attempt to get around that limitation.

The use case where I was able to get it to show up most dramatically is when there are a few thousand segments in a topN query with populate cache enabled.