The method `initiateChannel` on `TcpTransport` is explicit in that
channels can be connect asynchronously. All production implementations
do connect asynchronously. Only the blocking `MockTcpTransport`
connects in a synchronous manner. This avoids testing some of the
blocking code in `TcpTransport` that waits on connections to complete.
Additionally, it requires a more extensive method signature than
required for other transports.
This commit modifies the `MockTcpTransport` to make these connections
asynchronously on a different thread. Additionally, it simplifies that
`initiateChannel` method signature.
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.