fix(sources): Shutdown starting from `tcp` and `unix` sockets (#2618)

* Add ReadUntil

Signed-off-by: Kruno Tomola Fabro <krunotf@gmail.com>

* Fix mock source

Signed-off-by: Kruno Tomola Fabro <krunotf@gmail.com>

* Fix mock source

Signed-off-by: Kruno Tomola Fabro <krunotf@gmail.com>

* Rename

Signed-off-by: Kruno Tomola Fabro <krunotf@gmail.com>

* Rename struct

Signed-off-by: Kruno Tomola Fabro <krunotf@gmail.com>

* Simplify assert

Signed-off-by: Kruno Tomola Fabro <krunotf@gmail.com>

* Trigger write shutdown

Signed-off-by: Kruno Tomola Fabro <krunotf@gmail.com>

* Add test & fix TcpSink

Signed-off-by: Kruno Tomola Fabro <krunotf@gmail.com>

* Remove stray comment

Signed-off-by: Kruno Tomola Fabro <krunotf@gmail.com>

* Bump

Signed-off-by: Kruno Tomola Fabro <krunotf@gmail.com>