MAJOR: stream/conn_stream: Move the stream-interface into the conn-stream

Thanks to all previous changes, it is now possible to move the
stream-interface into the conn-stream. To do so, some SI functions are
removed and their conn-stream counterparts are added. In addition, the
conn-stream is now responsible to create and release the
stream-interface. While the stream-interfaces were inlined in the stream
structure, there is now a pointer in the conn-stream. stream-interfaces are
now dynamically allocated. Thus a dedicated pool is added. It is a temporary
change because, at the end, the stream-interface structure will most
probably disappear.
diff --git a/src/hq_interop.c b/src/hq_interop.c
index 376779d..c9d8c9a 100644
--- a/src/hq_interop.c
+++ b/src/hq_interop.c
@@ -72,10 +72,10 @@
 	htx_add_endof(htx, HTX_BLK_EOH);
 	htx_to_buf(htx, &htx_buf);
 
-	cs = cs_new(&qcs->qcc->conn->obj_type);
+	cs = cs_new();
 	if (!cs)
 		return -1;
-
+	cs_attach_endp(cs, &qcs->qcc->conn->obj_type, qcs);
 	cs->ctx = qcs;
 	stream_create_from_cs(cs, &htx_buf);