This commit is related to #27260. It moves the TcpChannelFactory into
NioTransport so that consumers do not have to be passed around.
Additionally it deletes an unused read handler.
This is related to #27260. This commit moves the NioTransport from
:test:framework to a new nio-transport plugin. Additionally, supporting
tcp decoding classes are moved to this plugin. Generic byte reading and
writing contexts are moved to the nio library.
Additionally, this commit adds a basic MockNioTransport to
:test:framework that is a TcpTransport implementation for testing that
is driven by nio.
Tim Brooks