[FEA] java HostMemoryBuffer should mirror copy functions in BaseDeviceMemoryBuffer

We have some places where we would like a host buffer to be able to copy:
1. Given a source/destination offset
2. Given a stream
3. From host or from device buffers.

Currently `HostMemoryBuffer` does allow wholesale copies of device buffers, and even using a stream, but there is no way I can find to do this at an offset. I can think of ways of hacking around it, but it would be best if the APIs were similar for both buffer types.