Allow controls with --no-window

Without a window, mouse and keyboard events may not be received, but
the control channel is still necessary for other features:

 * --turn-screen-off
 * --stay-awake
 * --show-touches
 * --power-off-on-close
 * --start-app

Fixes #5803 <https://github.com/Genymobile/scrcpy/issues/5803>
PR #5804 <https://github.com/Genymobile/scrcpy/pull/5804>

Signed-off-by: Romain Vimont <rom@rom1v.com>