|ReceiveSocketData| receives socket data on the main thread. This
is a specific detail of the current socket classes, which should not
be required by future implementations.
This patch moves the receive method and the corresponding runnable
into socket classes.
This patch renames |SocketConsumerBase| to |DataSocket|, and for the
I/O classes |SocketConsumerIO| to |DataSocketIO|. |DataSocketIO| also
contains send and receive functionality from |SocketBaseIO|.
|DataSocket| is a virtual base class that represents a socket that
transfers data, without a particular constraints to what the data
represents. |DataSocketIO| is the corresponding helper class on the
I/O thread.