MEDIUM: mux-h1: Handle errors and timeouts in the stream

MEDIUM: mux-h1: Handle errors and timeouts in the stream

To do so, the stream is created as earlier as possible. It means, during the mux
creation for the first request, and for others, just at the end of the previous
transaction. Because all timeouts are handled by the strream, the mux's task is
now useless, so it is removed. Finally, to report errors, flags are set on the
HTX message. The HTX message is passed to the stream if there is some content to
analyse or if there is some error to handle.

All of this will probably be reworked later to handle errors and timeouts
directly in the mux. For now, it is the simpler way to handle all of this.